Medium access control protocols for wireless LANs [guest editorial]

The six papers in this special issue focus on medium access control protocols for wireless LANs. The papers are summarized here.     

Speech multiplexing in wireless PCS employing resource auction multiple access (RAMA)

The excess capacity of the access mechanism in resource auction multiple access (RAMA) is evaluated for statistical multiplexing of speech. The aim is to exploit this excess capacity to increase the number of subscribers for a given bandwidth. It is shown that, for packet dropping probabilities of 1%, RAMA can have a multiplexing gain as high as 2.56 with fast speech detection and 2.2 with slow speech detection. The simulation results also indicate that RAMA is suitable for fast handoffs and resource allocation with statistical speech multiplexing over areas with a wide variety of cell sizes.<>     

Hybrid prioritized multiple access protocols for bank LANs

Bank communication networks support four classes of traffic: Alarm, BSC, SNA and IP traffic, with each class of traffic having different priority requirements. In this paper, a framework for the design of multiple access protocols which are capable of handling the above priority classes is introduced. Furthermore, a hybrid multiple access protocol that has been designed according to the proposed framework is presented and evaluated by means of extensive simulation results. The proposed protocol, is applicable to a broad range of prioritized LANs. Copyright © 2004 John Wiley & Sons, Ltd.     

Low-complexity multiple access protocols for wavelength-divisionmultiplexed photonic networks

Media access control protocols for an optically interconnected star-coupled system with preallocated wavelength-division multiple-access channels are discussed. The photonic network is based on a passive star-coupled configuration in which high topological connectivity is achieved with low complexity and excellent fault tolerance. The channels are preallocated to the nodes with the proposed approach, and each node has a home channel it uses either for data packet transmission or data packet reception. The performance of a generalized random access protocol is compared to an approach based on interleaved time multiplexing. Semi-Markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through extensive simulation. The performance is evaluated in terms of network throughput and packet delay with variations in the number of nodes, data channels, and packet generation rate     

Prioritized slotted multiple access protocols for bank LANs

Four classes of traffic are present in a bank communication system: Alarm, BSC, SNA and IP traffic, with each class of traffic having different priority requirements. In this paper, a prioritized multiple access protocol is introduced which is capable of handling the above priority classes. The proposed protocol makes use of learning automata in order to dynamically assign the available bandwidth to the priority classes. In this way, it is capable of being adapted to the traffic conditions. The proposed protocol, is applicable to a broad range of prioritized LANs, as it can be easily extended to support multiple classes of traffic. Copyright © 2003 John Wiley & Sons, Ltd.     

An overview of MIMO-oriented channel access in wireless networks [medium access control protocols for wireless LANs]

The integration of MIMO technology in WLANs has recently been the locus of extensive research. The main objectives of this technology are to improve channel reuse and or reduce energy consumption. In this article, we give an overview of MIMO systems and their use in WLANs. We highlight the different types of gains that MIMO offers and then discuss some of the work that has been done on MAC design. We conclude by outlining several open issues thai must be addressed for MIMO-based systems.     

Performance analysis of multiple access protocols for multimediasatellite networks

In this paper, several TDMA-based packet multiple access protocols are studied and evaluated in the geostationary satellite environment. The distributed queueing random access protocol, DQRAP, originally proposed for HFC networks is adapted to the satellite environment. Another protocol, the announced retransmission random access protocol, ARRA, proposed for wireless networks is also studied. Both protocols are modeled and simulated in a VSAT network context. We then propose a new protocol which combines the advantages of both studied schemes and is more adapted to interactive multimedia applications over satellite uplinks. The generalized retransmission announcement protocol, GRAP, regroups the immediate access by contention at low loads, and the reservation access. At higher loads, to achieve a better channel efficiency. An analytical model is proposed to calculate the channel throughput obtained by GRAP under different loading conditions. Simulation results illustrate an improved throughput/delay characteristics and a higher protocol stability compared to both DQRAP and ARRA. Enhanced versions of the protocol are also proposed and evaluated to further improve its efficiency, with reasonable additional complexity     

On the capacity of infinite population multiple access protocols

We present bounds on the maximum channel utilization (with finite average delay) of synchronous multiple access communications protocols serving an infinite population of homogeneous stations. Messages arrive to the system as a series of independent Bernoulli trials in discrete time, with probability p of an arrival at each arrival point (the Poisson limit is explicitly included) and are then randomly distributed among the stations. Pippenger showed that the channel utilization cannot exceedxi_{p}, wherexi_{l}=1andlim_{p rightarrow 0} xi_{p} approx 0.744. Using a "helpful genie" argument, we find the exact capacity for allp geq 0.568(where we find optimal protocols that obey first-come first-served); for smaller values of p, we present an improved upper bound that decreases monotonically toapprox 0.6731in the Poisson limit asp rightarrow 0.     

Cutoff points for roll call protocols in multiple access systems

A communication network with multiple users sharing a common broadcast channel is considered. Ak-channel is defined to be a channel that can carry up tok-1successful transmissions simultaneously, but simultaneous transmissions bykor more users cause a collision and no successful transmissions take place. The question arises as to how to organize transmissions to avoid collisions or to resolve them efficiently when they occur. The most conservative approach is to use a roll call scheme, which guarantees that collisions never occur. However, other approaches may sometimes be more efficient. It is supposed that each user has the same probabilitypof wanting to transmit, and for several different models the conditions onpunder which roll call is the most efficient scheme for ak-channel are determined.     

A quantitative comparison of multiple access control protocols forwireless ATM

The multiple access control (MAC) problem in a wireless network has intrigued researchers for years. For a broad-band wireless network such as wireless ATM, an effective MAC protocol is very much desired because efficient allocation of channel bandwidth is imperative in accommodating a large user population with satisfactory quality of service. Indeed, MAC protocols for a wireless ATM network in which user traffic requirements are highly heterogeneous (classified into CBR, VBR, and ABR), are even more intricate to design. Considerable research efforts expended in tackling the problem have resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how time different protocols compare against each other on a unified basis. In this paper, we quantitatively compare seven previously proposed TDMA-based MAC protocols for integrated wireless data and voice services. We first propose a taxonomy of TDMA-based protocols, from which we carefully select seven protocols, namely SCAMA, DTDMA/VR, DTDMA/PR, DQRUMA, DPRMMA, DSA++, and PRMA/DA, such that they are devised based on rather orthogonal design philosophies. The objective of our comparison is to highlight the merits and demerits of different protocol designs     

Afterburner [network-independent card for protocols]

Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented     

Performance comparison of battery power consumption in wireless multiple access protocols

Energy efficiency is an important issue in mobile wireless networks since the battery life of mobile terminals is limited. Conservation of battery power has been addressed using many techniques such as variable speed CPUs, flash memory, disk spindowns, and so on. We believe that energy conservation should be an important factor in the design of networking protocols for mobile wireless networks. In particular, this paper addresses energy efficiency in medium access control (MAC) protocols for wireless networks. The paper develops a framework to study the energy consumption of a MAC protocol from the transceiver usage perspective. This framework is then applied to compare the performance of a set of protocols that includes IEEE 802.11, ECMAC, PRMA, MDRTDMA, and DQRUMA*. The performance metrics considered are transmitter and receiver usage times for packet transmission and reception. The time estimates are then combined with power ratings for a Proxim RangeLAN2 radio card to obtain an estimate of the energy consumed for MAC related activities. The analysis here shows that protocols that aim to reduce the number of contentions perform better from an energy consumption perspective. The receiver usage time, however, tends to be higher for protocols that require the mobile to sense the medium before attempting transmission. The paper also provides a set of principles that could be applied when designing access protocols for wireless networks.*ECMAC: energyconserving MAC. PRMA: packet reservation multiple access. MDRTDMA: multiservices dynamic reservation TDMA. DQRUMA: distributedqueuing request update multiple access.     

Tradeoffs: turf vs. togetherness [ESPRIT]

The changes that will attend the creation of a single European market in 1992 and the tradeoffs entailed are discussed. The biggest success so far has been so-called precompetitive research, which began with the advent of the European Strategic Programme for Research and Development in Information Technology (ESPRIT) in 1984. The ESPRIT program, and the dozens of others created in its image, are making progress toward two goals fundamental to the ultimate goal of unification. Research has also assumed the more concrete role of helping to reform Europe's industries by moving them toward the single market, particularly in telecommunications. The existence of 12 telephone networks with vastly different technologies presents a huge obstacle to a single market     

A near-optimum cross-layered distributed queuing protocol for wireless LAN [medium access control protocols for wireless LANs]

Distributed queuing collision avoidance (DQCA) is a distributed MAC protocol for WLAN systems that offers near optimum performance. The protocol implements a reservation scheme that ensures collision-free data transmissions for high traffic load and switches smoothly and automatically to a random access mechanism when the traffic load is light, improving the delay performance for this situation. In this article the DQCA protocol operation is thoroughly described, and its algorithm rules are given. Furthermore, an enhanced cross-layer scheduling mechanism is also proposed for inclusion in the protocol procedure. This mechanism employs a virtual priority function to reschedule transmissions according to a cross-layer design. Two possible configurations are described in this article by including a PHY-MAC dialog involving channel stale information and the waiting time of the packets in the system, offering a trade-off between throughput maximization and fairness. The performance in terms of throughput and mean delay of DQCA and the two cross-layer schemes has been evaluated through simulations, and a significant enhancement over legacy IEEE 802.11 operation is achieved. The obtained results emphasize the advantages of the proposed schemes and the importance of cross-layer design in wireless communication systems.     

MCCA: a high-throughput MAC strategy for next-generation WLANs [medium access control protocols for wireless LANs]

Wireless LAN technology has been shown to he a revolutionary development during the last decade. Recently popularized IEEE 802.11a/g-based products can support up to 54 Mb/s physical layer rate and provide wireless access to the Internet. However, in order to deal robustly with the unreliable wireless nature, the 802.11 medium access control protocol has a relatively large overhead and hence, the throughput performance is much worse than the underlying physical layer rate. Moreover, along with many emerging applications and services over WLANs, such as voice over WLAN and audio/video streaming, the demand lor faster and higher- capacity WLANs has been growing recently. In this article, we propose a new medium access control protocol for the next-generation high-speed WLANs. The proposed medium access control, called multi-user polling controlled channel access, is composed of two components: multi-layer frame aggregation, which performs aggregation at both the medium access control and the physical layers; and multi-user polling, used to reduce the contention overhead and in turn, achieve higher network utilization. Multi-user polling controlled channel access is compared with the 802.11e-enhanced distributed channel access medium access control. Highly enhanced medium access control efficiency can be achieved by applying multi-user polling controlled channel access. We show the improved medium access control performance in terms of the aggregate throughput of non-QoS Hows with relevant QoS requirements.     

Frequency-domain precoding for single carrier frequency-division multiple access - [topics in radio communications]

At present there is considerable interest in the use of single carrier frequency-division multiple access. This interest is justified by the inherent single carrier structure of the SC-FDMA scheme, which is more robust against phase noise and has a lower peak-to-average power ratio than orthogonal frequency-division multiple access. This consequently makes it more attractive for uplink transmission from low-cost devices with limited transmit power. SC-FDMA commonly makes use of frequency domain linear equalization in order to combat the frequency selectivity of the transmission channel. Frequency domain decision feedback equalization, composed of a frequency domain feed forward filter and a time domain feedback filter, outperforms LE due to its ability to cancel precursor echoes. Although these solutions suffer from error propagation, results show that DFE still offers a significant performance gain over conventional LE for uncoded SC-FDMA. In this article we show how precoding can be used on the uplink of the LTE standard to overcome the frequency selective nature of the radio channel. We propose a frequency domain implementation of Tomlinson- Harashima precoding and investigate the bit error rate and the PAPR performance for SCFDMA using ZF and MMSE THP.