Multiaccess Protocol Research Articles

Optimal broadcast scheduling in packet radio networks using mean field annealing

We present an efficient broadcast scheduling algorithm based on mean field annealing (MFA) neural networks. Packet radio (PR) is a technology that applies the packet switching technique to the broadcast radio environment. In a PR network, a single high-speed wideband channel is shared by all PR stations. When a time-division multi-access protocol is used, the access to the channel by the stations' transmissions must be properly scheduled in both the time and space domains in order to avoid collisions or interferences. It is proven that such a scheduling problem is NP-complete. Therefore, an efficient polynomial algorithm rarely exists, and a mean field annealing-based algorithm is proposed to schedule the stations' transmissions in a frame consisting of certain number of time slots. Numerical examples and comparisons with some existing scheduling algorithms have shown that the proposed scheme can find near-optimal solutions with reasonable computational complexity. Both time delay and channel utilization are calculated based on the found schedules.

Implications of physical layer overhead on the designof multiaccess protocols

The authors examine the implications of physical layer overhead on the design of multiaccess protocols under a demand-assignment framework, comparing full-slot contention with mini-slot contention. Even if the physical layer overhead is substantial relative to the packet size, we show that after ‘paying the price’ of transmitting the physical layer overhead it is still better, from a delay-throughput perspective, to only transmit a short request rather than a full packet during a contention period.

Dynamic control of time slot assignment in multiaccess reservation protocols

The authors consider the dynamic control of time slot assignment in reservation protocols for multiaccess channels employing frame structures similar to those investigated by Roberts and others. Such protocols are particularly suitable for channels with long propagation delays, such as satellite channels. Fixed length frames are dynamically divided on a frame by frame basis into reservation subframes with minislots for reservation requests transmitted by slotted Aloha random access, and data subframes with reserved time slots for data packet transmissions. Formulating the problem as a Markov decision process, the authors derive the optimal time slot assignment policy, which makes use of complete state information of the finite user population, and obtain the delay-throughput performance. Results show that the optimal policy provides substantial performance improvements over fixed assignment policies. Furthermore, a heuristic dynamic assignment policy called the MF policy is proposed that is much easier to derive and implement, particularly for large networks, while maintaining performance very close to the optimal. Both of these dynamic policies depend on system state information, which the authors propose to estimate using a generalised pseudo-Bayesian estimator. The use of this estimator results in only a small reduction in performance.

Networks of low-Earth orbit store-and-forward satellites

A slotted multiaccess protocol is proposed for networks of low-Earth orbit store-and-forward communications satellites. Networks of this type would provide communication between low cost geographically distributed Earth stations, and would be particularly attractive in areas where conventional terrestrial communications systems were not available. Applications of this type include data acquisition and remote process monitoring. The proposed protocol incorporates time division multiplexing (TDM) on the downlink, slotted Aloha with collision resolution on the uplink, and an automatic repeat request (ARQ) algorithm. Since the network connectivity is intermittent, analysis of networks of this type is difficult. Nevertheless, relationships among the performance parameters for a general network are deduced, and performance of three particular network configurations is studied via simulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reducing global address recognition delays in local area networks with spatial bandwidth reuse

Abstract A special class of local area networks have recently received much attention in which destination nodes remove packets from the network, allowing spatial bandwidth reuse or concurrent transmission of packets without collision. Destination removal requires that each node delay packets long enough so it can decode the destination address. If the address is a short label (say, 8-bit) the decoding time is short, but if we want to use global or MAC addresses of 48 or 64 bits, the sum of decoding times encountered by packets may result in unacceptably long delays, even at light traffic loads. In this paper, we propose protocols for reducing global address recognition delays which are designed to supplement existing protocols for local area networks with spatial bandwidth reuse. They are also designed to coexist with other addressing modes used for individual LANs, which are based on the use of very short, locally administered labels. Of particular interest is a completely decentralized protocol which achieves the low global address recognition delays of multi-access protocols and yet seamlessly reverts to efficient spatial bandwidth reuse at high loads. We focus on the MetaRing and MetaNet architectures and apply our methods to these local area networks. A simple probabilistic model is presented which demonstrates significant improvement in delay when our protocols are used.

Performance analysis of reservation random access protocols for wireless access networks

A key issue in future wireless access networks is the design of multiaccess protocols that enable dispersed voice and data terminals to efficiently share the terminal-to-base radio channel. A promising class of multiaccess protocols for wireless access is that of reservation random access (RRA) protocols, in which voice talkspurt packets and data packets are statistically multiplexed over TDMA frames. Voice terminals obtain reservations for their talkspurts using a random access protocol. An analysis method for evaluating the performance of a class of RRA protocols is developed. The method is based on a Markovian model, whose stationary solution is obtained via an iterative computational procedure based on matrix decomposition techniques. Subject to a maximum delay constraint, the voice packet dropping rate and distribution of the number of packets dropped from a talkspurt are evaluated for three RRA protocol examples, and comparisons are made with the performance of an ideal hypothetical multiplexer. The transient performance of RRA protocols is evaluated by simulating their response to sudden changes in the number of active voice terminals. Finally, suggestions for the design of integrated voice/data RRA protocols are made. >

Voice/data channel access integration in TDMA digital cellular networks

The integration of digital data capabilities in the soon to be widely deployed digital cellular networks, which were primarily designed for voice communications, offers a low-cost way to capture the large and ever growing market for mobile data services. The authors propose and evaluate a multiaccess protocol for integrating data traffic in the E(nhanced)-TDMA voice system with digital speech interpolation, which is an enhancement of the emerging North American digital cellular standard. The proposed, protocol combines random access with slot reservation mechanisms to statistically multiplex data packets with speech spurt packets over the shared terminal-to-base air channel. The integrated protocol requires no modification in the voice access protocol used in the E-TDMA system, and can attain performance close to that of an ideal voice/data multiplexer. Furthermore, the protocol may enable multislot assignment per TDMA frame to match the throughput needs of individual data terminals, and can accommodate application-dependent data transmission priorities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The tone sense multiaccess protocols with partial collision detections (TSMA/PCD) for packet satellite communications

The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N=10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N=8 and N=2, respectively, are sufficient to drive the system to the CSMA/CD performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Packet reservation protocols for multichannel satellite networks

Owing to system economics, many satellite data networks have star configurations, with low cost user terminals communicating with high performance hub earth stations over inbound multiaccess channels and outbound broadcast channels. The inbound channel data rate is often limited by the power budget, so that multiple satellite channels are required to accommodate the overall traffic in a large network. Most packet multiaccess protocols previously considered, when applied to multichannel satellite networks, enable distinct groups of users to share individual channels. In contrast, this paper presents a new class of multichannel reservation protocols (MRPs) which improves channel utilisation by enabling complete sharing of all channels among all users. For good throughput efficiency and reduced delay, the MRPs employ slotted random access with immediate retransmissions for first-packet and reservation request transmissions, and reservation of consecutive time slots for transmissions of remaining packets in multipacket messages. Delay throughput characteristics are derived under steady state conditions. Numerical results show that the MRPs achieve higher throughput capacity than random access protocols and lower average delay than other reservation protocols.

Design of an Optimum Channel Utilisation Multiaccess Protocol for Packet Radio Networks

Design and throughput performance of an Optimum Channel Utilisation Multiaccess (OCUM) protocol applicable to Packet Radio Networks (PRN) is presented in this paper. The OCUM protocol utilizes a slotted message channel for data transmission and a busytone channel for sensing and acknowledgement functions. The messages constitute multiple data packets where each packet length is equal to one slot size. The OCUM protocol design results in effective utilisation of the message channel by achieving minimum channel idle rate and collision rate. The throughput performance of the protocol has been analyzed for a finite population model with Bernoulli arrivals at cach node, geometric distribution of message lengths (measured in number of packets) and with no buffer assumption. Both the analytical and simulation results show that the protocol enjoys better throughput characteristics at high values of average message lengths making it ideally suited for file transfer type applications.

Status sense multiple-access (S/sup 2/MA) communication

A new contention-based multi-access protocol, named status sense multiple access (S/sup 2/MA), is introduced. S/sup 2/MA is synchronous TDMA in its framing but it possesses many features of random access. The approach of S/sup 2/MA is geared towards integrating heterogeneous classes of customers over a common broadcast channel. The performance of this protocol with two classes of customers, such as voice and data, is analyzed. Unlike fixed and some moveable-boundary approaches of integrating voice and data, here no slot is wasted, except for possible collision, as long as there is a demand for the slot from either of the two classes. Therefore, the channel utilization efficiency can be very high. >

Design and analysis of an MAC-layer protocol for a car-to-infrastructure packet radio network

The structure of a packet radio network that must operate in an environment characterized by the presence of mobile stations and a ground network with fixed access points is defined. Each of these points consists of a ground station with a certain coverage area, which must exchange data with the mobiles over a common radio channel. Mobiles within the coverage area of a ground station must coordinate their access to the common channel. The design and analysis of the multiaccess protocol is considered, together with the procedure for the passage from a ground station coverage area to the next one along the direction of flow. The overall access strategy is described and analyzed to some extent, and simulation results are provided. The integration of this medium access control (MAC) layer protocol with existing packet radio software that also covers higher layer features is also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Diversity reservation ALOHA

A multiaccess protocol suitable for packet satellite broadcast channels is introduced in this paper. The proposed protocol, called diversity reservation ALOHA (DRA) combines the essential features of announced retransmission random access (ARRA). diversity ALOHA, and a reservation scheme with a slotted ALOHA reservation channel to achieve the goals of improved delay-throughput characteristics and high channel utilization. Two versions of DRA protocols are analyzed. In scheme 1, called DRA with reservation cleared (DRA-RC), no global queue information is required for a user to access the channel. In this version, even a successful transmission of reservation requests will be cleared from the system if it causes overflow. The second scheme, called DRA with reservation delayed (DRA-RD), establishes a global queue distributed at users' terminals, so that users with successful transmission of reservation requests are assured of access rights although transmission may be delayed to later fames. Important system performance measures, such as activity-factor-throughput characteristics, for DRA-RC and DRA-RD are compared with those of ARRA. Examples of numerical results show that with system parameters properly chosen, substantial increases in attainable channel utilization are possible. Furthermore, the use of diversity for reservation allows a smaller packet delay especially under light traffic conditions. The analysis is validated in light of the simulation results.

A controlled multiaccess protocol for packet satellite communication

This protocol is fully distributed and no onboard processing is required for the satellite. A control parameter f is used to adaptively control the packet transmission rate such that maximum system capacity can be attained and the average delay is always minimized for a given throughput. The controlled protocol is found to give a smaller average delay than slotted ALOHA even when the throughput is as low as 0.05. On the other hand, under heavy traffic conditions, it can provide a throughput close to unity and an average delay not much more than one round-trip propagation delay. The system performance is also robust, in the sense that a 15% error in throughput estimation results in no more than a 3% increase of the overall average packet delay. >

A media-access protocol for packet-switched wavelength division multiaccess metropolitan area networks

A dynamic time-wavelength division multiaccess protocol (DT-WDMA) is proposed for metropolitan-sized multichannel optical networks employing fixed wavelength transmitters and tunable optical receivers. Control information is sent over a dedicated signaling channel and data are sent over channels owned by the transmitters. Time is divided into slots on each channel and slots on the control channel are further split into mini-slots. Fixed time-division multiaccess (TDM) is used within each slot on the control channel. Transmitters indicate their intention to transmit a packet by transmitting the destination address during their appropriate mini-slot in the control channel and then transmit their packet in the next slot on their data channel. Receivers listen to the control channel and tune to the appropriate channel to receive packets addressed to them. A common but distributed arbitration algorithm is used to resolve conflicts when packets from many transmitters contend for the same receiver. Each receiver executes the same deterministic algorithm to choose one of the contending packets. Each transmitter uses the same algorithm to determine the success or failure of its packet. >

Selective reject ALOHA/FCFS: An advanced VSAT channel access protocol

AbstractThis paper proposes and evaluates selective reject (SREJ) ALOHA/FCFS, a highly efficient, flexible and robust multiaccess protocol for very small aperture terminal (VSAT) applications. SREJ‐ALOHA with locally synchronous FCFS retransmission scheduling is a ‘semi‐compatible’ enhancement of asynchronous SREJ‐ALOHA, which has earlier been shown to be an attractive satellite channel sharing protocol for low volume bursty terminals with variable length messages. The FCFS retransmission scheduling policy proposed here broadens the applicability of SREJ‐ALOHA by providing higher maximum throughput, particularly in the important source traffic scenario with bimodal message length distributions. Improved channel‐sharing efficiency and delay are achieved by exploiting time‐of‐arrival feedback naturally embedded in an unslotted SREJ‐ALOHA channel to develop an implicit time‐of‐arrival based (FCFS) ordering for conflict‐free, locally synchronous retransmission of most contending messages. An analytical procedure for evaluation of stability, throughput and delay for a general finite source, variable message length traffic model is described. The model is used to demonstrate that random access SREJ‐ALOHA/FCFS typically achieves a maximum throughput in the region of 0·4–0·45 along with excellent stability and delay properties. In addition, a natural extension of the protocol which supports implicit reservation for long messages is described and shown to offer a high maximum throughput (&gt;0·6), comparable to that achieved by highly co‐ordinated slotted systems, for example mixed interactive/file‐transfer traffic scenarios.

Rule-based network design: application to packet radio networks

A heuristic, rule-based approach to network design is presented. The problem of designing high-performance packet radio networks by altering individual radio powers (i.e. by altering network connectivity) is considered. It is assumed that node locations, traffic requirements, and a multiaccess protocol are specified. The focus is on the dependence of capacity on connectivity for two reasons: connectivity is always a design parameter, whereas radio locations, protocol, and traffic may not always be; and the relationship between capacity and connectivity is well documented in the literature, even though the exact nature of this reliance remains unclear. Packet radio performance analysis models found in the literature are used for performance evaluation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance evaluation of extended token bus protocol

The semi-Markov performance model of a bus protocol (IMAP—improved token bus multi-access protocol), suitable for embedded networks, is presented. IMAP is an improvement over the token bus scheme, and has been proposed by Sood et al. (1986). The semi-Markov model is developed by considering the normal and interrupt modes of operation of IMAP. The performance of IMAP is compared to that of the token bus scheme.

On improving throughput in packet mobile radio network

A novel random multiaccess protocol is proposed for a packet mobile-radio network employing an idle-signal casting multiple-access (ICMA) with/without collision detection scheme. The protocol takes advantage of the channel control scheme to reduce collisions. The authors show significant improvements in terms of maximum achievable throughput. >

The scheduled-retransmission multiaccess (SRMA) protocol for packet satellite communication

An improvement of the announced retransmission random access (ARRA) protocol for packet satellite communication, called the scheduled retransmission multiaccess protocol, is introduced. Besides avoiding collision between new and retransmitted packets, the improved protocol eliminates reservation conflicts between different slots. Explicit acknowledgement is used, so that traffic to other zones served by the same satellite can also be accommodated. Assuming that 3% of the channel capacity is used for retransmission reservation, fixed frame and dynamic-frame SRMAs achieve effective maximum throughputs of 0.65 and 0.89, respectively. Both protocols give average delays considerably lower than slotted ALOHA, even when the throughput is as low as 0.2.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>