Channel Access Protocol Research Articles

Properties of a transmission assignment algorithm for multiple-hop packet radio networks

We study an algorithm, originally defined by Lyui (1991), for assigning collision-free broadcast transmissions for packet radio networks. The method has a number of advantages - it is distributed, fair, permits each terminal to calculate a different frame size, requires only a limited exchange of information, and does not require a contention-based channel-access protocol. These properties make the assignment algorithm particularly useful for dynamic ad hoc networks because the transmission assignments can be easily and quickly adapted to local changes in the topology. An improved description of Lyui's algorithm is given and new simulation results are presented to demonstrate the properties of the transmission assignments for a variety of large networks.

Robustness of Q-ary collision resolution algorithms in random access systems

The throughput characteristics of a random access system (RAS) which uses Q-ary tree algorithms (where Q is the number of groups into which colliding users are split) of the Capetanakis–Tsybakov–Mikhailov–Vvedenskaya type are analyzed for an infinite population of identical users generating packets. In the standard model packets are assumed to be generated according to a Poisson process. In this paper we greatly relax this assumption and consider a rich class of Markovian arrival processes, which, in general, are non-renewal. This class of arrival processes is known to lend itself very well to modeling bursty and correlated arrival processes commonly arising in computer and communication applications. Blocked and grouped channel access protocols are considered in combination with Q-ary collision resolution algorithms that exploit either binary (“collision or not”) or ternary (“collision, success or idle”) feedback. For the resulting RASs the corresponding maximum stable throughput is determined. It is concluded that the resulting RASs maintain their good stability characteristics under the wide range of arrival processes considered, thereby further extending the theoretical foundations of tree algorithms.

Performance analysis of an enhanced DQRUMA/MC-CDMA protocol for voice traffic

The original distributed-queueing request update multiple-access (DQRUMA)/multicode code-division multiple-access (MC-CDMA) protocol was developed as a channel access protocol for wireless packet CDMA networks. This protocol has recently attracted considerable attention. We modify the original protocol, which was designed for data traffic only, to additionally accommodate voice traffic and call it the A-Protocol. We propose a new packet CDMA protocol that enhances the A-Protocol by improving the utilization of receivers in a base station and call it the E-Protocol. In the E-Protocol, an access request is attempted with a randomly chosen code at a request minislot. We analytically evaluate the performance of both protocols and compare analytical results with computer simulation. Analytical results agree well with simulation results.

On achieving fairness and efficiency in high-speed shared medium access

Channel access has been an active research area for the past two decades. Several protocols have been proposed in literature to efficiently utilize the channel bandwidth. Some of the recently proposed protocols achieve a near-ideal channel utilization. However, the efficiency in utilization comes at the expense of certain unfairness in delay characteristics. In this paper, a new channel-access protocol, called access mechanism for efficient sharing in broadcast medium networks (AMES-BM), is developed based on a deterministic binary tree-splitting technique to achieve efficient sharing of bandwidth. In AMES-BM, the stations are dynamically mapped to leaf nodes of a binary tree. The stations are then divided into smaller groups that mimic the behavior of an ideal transmission queue. Collisions are allowed to occur within these groups and are resolved using a variation of the conventional binary tree-splitting technique.The performance of AMES-BM is similar to that of a collisionbased protocol under low loads and to that of a collision-free protocol under high loads. Besides achieving a near-optimal channel utilization, the proposed protocol also guarantees fairness with respect to delay for messages of varying lengths. The deterministic nature of the protocol makes it more attractive for real-time applications.

Distributed dynamic channel access scheduling for ad hoc networks

Three types of collision-free channel access protocols for ad hoc networks are presented. These protocols are derived from a novel approach to contention resolution that allows contending entities to elect one or multiple winners for channel access in any given contention context (e.g., a time slot) in a distributed fashion. The only required information for each entity is the identifiers of its neighbors one and two hops away in the wireless network. The new protocols are shown to be fair and capable of achieving maximal utilization of the channel bandwidth. The delay and throughput characteristics of the contention resolution algorithms are analyzed, and the performance of the three types of channel access protocols is studied by simulations and compared with that of optimal static scheduling algorithms.

Design and Analysis of a Channel Access Protocol for WDM-Based Single-Hop Optical Networks*

We propose a channel access protocol for single-hop wavelength division multiplexing (WDM) optical networks. Each node is equipped with a fixed-tuned transmitter, a tunable transmitter, a fixed-tuned receiver, and a tunable receiver. The proposed protocol alleviates the drawbacks of a previous protocol [1], e.g., invalid data transmissions that follows receiver collisions and possible acknowledgment packet collisions with header/data packets, while retaining many advantages. As a result, the network performance in terms of throughput and packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the proposed protocol, and are validated through event-driven simulation. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Through numerical results and simulation studies, we show that the proposed protocol achieves better channel utilization and incurs lower packet delays.

Evaluation of a split-connection mobile transport protocol

A performance evaluation is presented for a split-connection protocol for wireless Internet access which is denoted Split-Connection Mobile Tranport Protocol (SCMTP). It uses the general approach of the previously introduced Mobile End Transport Protocol (METP) but with differences that include a wireless-link channel-access protocol better matched with current cellular networks and more general ARQ methods for error control in the wireless link. In common with METP, SCMTP uses a standard TCP protocol on the wireline connection and isolates the data flow in the wire-line network from the effect of wireless packet errors.Performance is considered for the important case of a single SCMTP split connection between a fixed host and a mobile host with heavy downlink traffic from the fixed host to the mobile host. It is shown for these conditions that if the wire-line packet-error rate is small, a steady state is reached in which the connection's data flow in the wire-line network remains under the control of the receiver-advertised window of the TCP entity at the base station. Performance is evaluated for the steady-state operation of the SCMTP protocol, and relationships are established between the key properties of the split connection and the end-to-end performance of the connection.It is shown that for heavy downlink traffic, the delay in the wire-line part of the connection does not affect steady-state throughput if the receiver buffer is sized appropriately. It is also shown that use of the go-back-N ARQ protocol on the wireless link yields better performance than the stop-and-wait ARQ protocol, although the performance with go-back-N ARQ is more sensitive to the characteristics of the wireless channel. It is shown that under a broad range of conditions, SCMTP with go-back-N ARQ provides nearly optimal utilization of the capacity of the wireless link.

Evaluation of channel access protocol performance for a mobile multimedia terminal in a multihop network

Evaluation of channel access protocol performance for a mobile multimedia terminal in a multihop network

Optimal transmission ranges and code rates for frequency-hop packet radio networks

We consider a frequency-hopping multihop packet radio network using M-ary frequency-shift keying modulation in a Rayleigh fading environment. Each node transmits packets using an extended (n, k) Reed-Solomon code and the slotted ALOHA channel access protocol. For this network, we determine the optimum transmission range, optimum code rate, and optimum slotted ALOHA transmission probability to be used by each node in the network. Tradeoffs in choosing the transmission range and code rate, and the spectral efficiency of the network are captured in a new performance measure, information efficiency, which is analogous to expected forward progress. Maximizing the information efficiency yields the optimum desired network parameters.

A New Token-Based Channel Access Protocol for Wavelength Division Multiplexed Multiprocessor Interconnects

This paper presents a new token-based channel access protocol for wavelength division multiplexed optically interconnected multiprocessors. Our empirical study of access protocols based on slotted time division multiplexed data and control channels reveals that such protocols typically suffer from excessive slot synchronization latency due to static slot preallocation. The proposed token-based time division multiple access protocol minimizes latency by allowing dynamic allocation of slots to use channels efficiently. Simulation results indicate that the proposed scheme can significantly increase the performance for protocols based on preallocation and also those based on preallocation-controlled reservation of multiple channels.

Evaluation of channel access protocol performance for a mobile multimedia terminal in a multihop network

The performance of the channel access protocol is a main factor when designing and evaluating the overall performance of a multimedia and multihop radio network. A search in the current open literature shows almost no results or investigation on this subject. The purpose of this research is to design and evaluate several candidates for the channel access protocol. The main objective is to find one, or more, protocol that can meet or exceed the performance requirements for all informed voice service to be provided by a hand-held mobile multimedia terminal (MMT) in a multihop network. Extensive simulation models of MMT have been developed using both asynchronous and synchronous protocol modes. The first one accesses the channel using a suitable random policy. The second one reserves time slots or periods in a fashion similar to conventional time division multiple access (TDMA) techniques. Within each mode there are several options involving various levels of implementation complexity. Based on the simulation results, the following recommendations and conclusions are made: (i) use an asynchronous policy that meets the requirements for all informed voice. At least one of the options studied and simulated meets those requirements; (ii) design a convenient mechanism to reserve channel capacity to ensure promised quality of service. This is particularly important for restricting the channel use for data streams on those nodes which are also handling voice packet streams; (iii) design practical methods to estimate channel capacity; (iv) the level of complexity for implementing any synchronous mode protocol greatly outweighs any potential network performance gain. No performance gain was observed with the synchronous mode procedure implemented in this research work; (v) refine the model to closely match the current design specification for the MMT system at the link layer level. Copyright © 2000 John Wiley & Sons, Ltd.

An unslotted multichannel channel-access protocol for distributed direct-sequence networks

A multichannel reservation-based channel-access protocol is investigated in this paper. The available system bandwidth is divided into distinct frequency channels. Under the protocol, one channel (the control channel) is used to exchange reservation messages and the remaining channels (the traffic channels) are used for information-bearing traffic. The performance of this scheme is compared to that of a single-channel reservation-based protocol. A simple contention-based slotted-Aloha protocol is also considered. Performance results take into account the effects of multiple-access interference on acquisition and packet errors. Results show that the reservation-based approach is advantageous under conditions of high traffic. In addition, a pacing mechanism that mitigates multiple-access interference and promotes fairness is described, and results are presented that demonstrate its effectiveness.

Architecture of a Terabit Free-Space Intelligent Optical Backplane

Optical technologies can support thousands of high bandwidth optical channels to/from a single CMOS integrated circuit, and can thus allow for the construction of novel bandwidth-intensive computing architectures which are no longer constrained by conventional electronic wiring limitations. In this paper, the architecture of a dynamically reconfigurableIntelligent Optical Backplaneis described. The backplane consists of a large number of parallel optical channels (typically 1000–10,000 bits) spaced a few hundred micrometers apart. The optical channels are arranged into upstream and downstream rings, where the channel access protocols are implemented by “smart pixel arrays.” The architecture exploits thebandwith advantageof the optical domain and can be dynamically reconfigured to embed conventional interconnection networks, including multiple busses, rings, and meshes. Unlike all-optical and passive optical systems, the proposed backplane is intelligent and can support communication primitives used in shared memory multiprocessing, including broadcasting, multicasting, acknowledgment, flow and error-control, buffering, shared memory caching, and synchronization. The backplane is also manufacturable using existing optoelectronic technologies. A second generation backplane supporting a distributed shared memory multi-processor is under development.

Optimal scheduling in cdma packet radio networks

Scope and Purpose—A packet radio network provides flexible data communication services among a large number of geographically distributed and mobile users (nodes). Organizing the multiple channel access in packet radio networks is a well known and widely discussed area. The time division multiple access (TDMA) technology has been popularly used and has been studied extensively. On the other hand, the development of the code division multiple access (CDMA) technology raises a new question in this field. In CDMA packet radio networks the channels can be realized by different orthogonal codes and the simultaneous reception of several packets is possible through the use of orthogonal codes. The multiple reception capacity provides an opportunity for significantly increasing system throughput. In this paper, we suggest an efficient heuristic algorithm for scheduling in CDMA packet radio networks. We consider the time slot assignment problem in a CDMA packet radio network. Unlike the classical TDMA packet radio networks, a CDMA packet radio network can provide each node with a multiple reception capacity using orthogonal codes. This multiple reception capacity of each node presents a new challenge for channel access protocols. Also we consider non-uniform traffic demand over nodes which has become important due to the increase of subscribers and the introduction of personal communication system (PCS). We present an algorithm for a general system where the number of nodes and the reception capacity can be any positive integers and the traffic demand can be non-uniform. Computational tests show that our algorithm generates excellent solutions in most cases.

Comparative analysis of wireless ATM channel access protocols supporting multimedia traffic

Extension of multimedia services and applications offered by ATM networks to wireless and mobile users has captured a lot of recent research attention. Research prototyping of wireless ATM networks is currently underway at many leading research and academic institutions. Various architectures have been proposed depending on the intended application domain. Successful implementation of wireless connectivity to ATM services is significantly dependent on the medium access control (MAC) protocol, which has to provide support for multimedia traffic and for quality-of-service (QoS) guarantees. The objective of this paper is to investigate the comparative performance of a set of access protocols, proposed earlier in the literature, with more realistic source traffic models. Data traffic is modeled with self-similar (fractal) behavior. Voice traffic is modeled by a slow speech activity detector (SAD). Video traffic is modeled as a H.261 video teleconference, where the number of ATM cells per video frame is described by a gamma distribution and a first-order discrete autoregressive process model. A comparison of the protocols based on simulation data is presented. The goal of the paper is to identify appropriate techniques for effectively and efficiently supporting multimedia traffic and QoS. Simulation results show that boundaries between different types of services are necessary for multimedia traffic. Reservation for certain traffic type especially video can significantly improve its quality. Reducing the number of collisions is an important issue for wireless networks since contentions lead not only to potentially high delay but also result in high power consumption.

New channel access protocol for a wide area DGPS deformation monitoring network

A new kind of one-point-to-multipoint random access channel protocol called the acknowledgement-type random access and code division multiple access channel protocol (ACK-ALOHA-CDMA) is presented. It is particularly applicable to the data transmission of differential global positioning system (DGPS) deformation or disaster monitoring networks with a large number of monitoring stations distributed over a wide area. The characteristics of the channel are analysed in detail and computer simulation results are given. Several mathematical functions and conclusions useful for both system design and performance evaluation are obtained.

A MULTIPLE-CHANNEL FREE-ACCESS COLLISION RESOLUTION ALGORITHM BASED CONNECTION REQUEST PROCEDURE FOR LAND MOBILE SATELLITE NETWORKS

A new binary feedback multiple-channel free-access (MCFA) collision resolution algorithm (CRA) based random-access protocol (RAP) is devised to implement the connection request procedure for demand-assigned channel access protocols in land mobile satellite communications networks. The maximum stable throughput of this protocol is derived and is shown to be superior to a previously devised multiple-channel obvious blocked-access CRA based RAP as well as to slotted ALOHA. The throughput performance is also superior to the previously devised multiple-channel window blocked-access CRA based RAP for four or more channels. An exact analysis of the average packet delay for this MCFA CRA based RAP is given and shown to be in excellent agreement with computer simulation results. The protocol is shown to have smaller average delays than the best single-channel free access CRA based RAPs over a wide range of practically usable throughput rates with reasonable delays. This MCFA CRA based RAP was implemented on a channel request protocol test-bed simulator which incorporates the physical link characteristics of the MSAT-X land mobile satellite system. These test-bed simulation results also demonstrate the superiority of this protocol over slotted ALOHA for both error-free channel and mobile facing channel scenarios.

An efficient demand-assignment multiple access protocol for wireless packet (ATM) networks

In a wireless packet (ATM) network that supports an integrated mix of multimedia traffic, the channel access protocol needs to be designed such that mobiles share the limited communications bandwidth in an efficient manner: maximizing the utilization of the frequency spectrum and minimizing the delay experienced by mobiles. In this paper, we propose and study an efficient demand-assignment channel access protocol, which we call Distributed-Queueing Request Update Multiple Access (DQRUMA). The protocol can be used for a wide range of applications and geographic distances. Mobiles need to send requests to the base station only for packets that arrive to an empty buffer. For packets that arrive to a non-empty buffer, transmission requests are placed collision-free by piggybacking the requests with packet transmissions. The simulation results show that even with the “worst possible” traffic characteristics, the delay-throughput performance of DQRUMA is close to the best possible with any access protocol. In addition, explicit slot-by-slot announcement of the “transmit permissions” gives the base station complete control over the order in which mobiles transmit their packets. This important feature helps the base station satisfy diverse Quality-of-Service (QoS) requirements in a wireless ATM network.

Use of GPS Time for Shared Satellite Channel Access

Synchronous channel access protocols like TDMA needs a global sync signal to be transmitted by a master station. All the other stations synchronize their transmission after receiving this signal. Instead of having a separate receive link at every station to receive the sync from the master station, each station can use globally available GPS time and access the channel synchronously. This method is useful to enhance the communication efficiency in applications like remote data collection platforms which has only one way communication link and has to depend only on random access protocol having much lower efficiency. This paper discusses the pros and cons of such an approach for INSAT based networks.

A multi-access scheme for voice/data integration in hybrid satellite/terrestrial packet radio networks

The paper examines protocols for voice/data integration in hybrid packet radio networks consisting of satellite and terrestrial components. The same protocols can be useful in the context of mixed-media packet radio networks employing HF ground radio links and EHF SATCOM radio links. As part of the integration protocol the ground subnetwork employs code-division multiple-access with movable boundary in the code domain to serve both the voice traffic and the retransmitted data traffic; on the satellite subnetwork framed ALOHA with movable boundary is used for both data and voice. A complete analysis of the channel-access protocols for both traffic types is provided based on a multi-dimensional Markovian model of the integrated voice/data system. The performance of the hybrid network is evaluated in terms of voice and data throughput, voice blocking probability, and data delay. It is observed that appropriate splitting of the retransmission traffic between the satellite and ground subnets may increase the overall data throughput when the voice load is high.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>