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.     

Cowry shell to smart card [electronic cash]

Cash, cheque, credit card, debit card, store card-methods of payment can seem bewildering in their variety. Here, the author describes how the Mondex system of electronic cash could bring order, convenience and security to the inescapable need to pay for goods and services     

E-BAMA vs. RAMA [multiple access protocols]

The article presents a performance comparison of two random access protocols for wireless mobile signaling in which a single channel is dedicated to the signaling function, enhanced beacon assisted multiple access (E-BAMA) and resource auction multiple access (RAMA). Data traffic is transported separately on a set of orthogonal channels. The beacon assisted multiple access (BAMA) protocol was first presented as a method of providing mobility management functions, e.g., handover, while minimizing the processing burden placed on the mobile. In BAMA, throughout the duration of its call, an active user repeatedly and quasi-periodically broadcasts a beacon containing its ID using the Aloha protocol. Quasi-periodicity prevents a pair of users from repeatedly colliding with each other. When a base successfully receives the beacon and assigns a channel, it uses a separate downstream channel to send to the mobile an acknowledgement that contains the number of the assigned channel. The BAMA protocol includes a scheme to maintain lists of active mobiles in nearby cells and to exchange periodically these lists among the base-stations. The authors evaluate the capacity and delay performance of E-BAMA and RAMA. Then, they present a numerical comparison of the parameters. Finally, the results are summarized qualitatively. Some additional derivation is included in the appendix     

Keyless entry system with radio card transponder [automobiles]

A keyless entry system for locking and unlocking vehicle doors, and for opening the trunk is described. This system utilizes a small (ordinary credit-card size) card transponder with a built-in personal identification code that can be carried in a pocket or a briefcase and the user does not have to take it out for use because the signal transmission is effected by inductive coupling between the card and loop antennas built into the door mirror housing and rear bumper. By touching a switch provided near the trunk keyhole, the user can open the door or trunk as if there were no locks. For anti-theft security and reliability, the system incorporates a twin-loop antenna that generates a rotating magnetic field, and a detection system to prevent the card transponder from being left inside the vehicle. This system has been installed in the luxury classes of Nissan models in the Japanese market     

Mobility management protocols for next-generation all-IP satellite networks [architectures and protocols for mobility management in all-IP mobile networks]

To provide ubiquitous terrestrial Internet coverage mobility and Internet-based access to data generated by satellites, there is a strong desire to integrate the terrestrial Internet and satellite networks. This requires satellites that are based on IP for communications. Rotation of low Earth orbit satellites around the Earth results in communicating with different ground stations over time, and requires mobility management protocols for seamless communication between the Internet and satellite networks. In this article we provide a comprehensive summary and comparison of state-of-the-art research on mobility management schemes for satellite networks. The schemes are based on network and transport layers for managing host and network mobility. This article clearly indicates the aspects that need further research and which mobility management schemes are the best candidates for satellite networks.     

Divestiture plus ten: an industry report card [telecommunication]

The factors driving change in the telecommunications industry since divestiture are examined. They are the customer, technology, the marketplace, and the public policy environment. It is concluded that progress in bringing new technologies, products, and services to the customer at reasonable prices is not progressing as well as it would if public policy restraints were removed and the free marketplace was allowed to operate     

Architectures and protocols for mobility management in all-IP mobile networks [guest editorial]

The seven Special Topic articles focus on the architectures and protocols for mobility management in all-IP mobile networks. The articles are summarized here.     

Comment on “Reparable key distribution protocols for Internetenvironments” [and reply]

For original paper see Hwang and Ku (IEEE Trans. Commun., vol.43, p.1947-9, 1995 May). The present authors find that the key distribution protocol KDP2 proposed in the original paper is, in fact, not reparable, as was claimed by the original authors. A reparable revised version of this KPD2 is then introduced. In a reply Hwang presents an example to show that the Lin et al. revised reparable KDP2 did not solve the problem which they proposed     

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.     

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.     

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.     

支持多种FC-4层协议的光纤通道接口卡实现

为满足航电网络中多种上层协议的应用需求,给出了一种支持包含IPFC(IP over Fibre Chan nel)、FC AV(Fibre Channe l Audio Video)、ASM(Anonymous SubscriberMessaging)的多种FC-4层协议的光纤通道(Fibre Channel,FC)接口卡的设计方案,并详细阐述了FC固件及PPC(Power PC)软件的实现方案。通过对接口卡的功能和性能测试,证明接口卡的通信符合协议要求,有较高的实时性和可靠性,为FC在航电领域的应用提供了参考。     

Variable bit rate VOiP in IEEE 802.11e wireless LANs [medium access control protocols for wireless LANs]

WLANs have become a ubiquitous networking technology deployed everywhere. Meanwhile. VoIP is one popular application and a viable alternative to traditional telephony systems due to its cost efficiency. VoIP over WLAN (VoWLAN) has been emerging as an infrastructure to provide low-cost wireless voice services. However, VoWLAN poses significant challenges due to the characteristics of contention-based protocols and wireless networks. In this article we propose two mechanisms to provide quality of service for variable bit rate VoIP in IEEE 802.11e contention-based channel access WLANs: access time-based admission control and access point dynamic access. Simulation results are conducted to study these schemes.     

Media-independent pre-authentication supporting secure interdomain handover optimization [architectures and protocols for mobility management in all-IP mobile networks]

Handovers may cause delays and packet losses that affect real-time communication performance. Mobility protocols at several layers are designed to support handover, but they need to be optimized to ensure high-quality application performance. Existing optimization techniques are not sufficient to take care of interdomain and intertechnology handovers involving different access technologies, such as Wi-Fi, GSM, CDMA, and WiMAX. We categorize several types of handover, describe handover delay components, and propose a handover optimization framework called media independent pre-authentication that can provide optimizations for interdomain and intertechnology handover in a manner that is transparent to mobility management protocols. In addition, we also present experimental results demonstrating that this framework can achieve a significant reduction in handover delays for both network-layer and application-layer mobility management protocols.