MAC Protocol Design Research Articles

DS/CDMA throughput of a multi‐hop sensor network in a Rayleigh fading underwater acoustic channel

AbstractAsynchronous half‐duplex Direct‐Sequence Code‐Division Multiple‐Access (DS/CDMA) is a suitable candidate for the MAC protocol design of underwater acoustic (UWA) sensor networks owing to its many attractive features. Our ad‐hoc multi‐hop network is infrastructureless in that it is without centralized base stations or power control. Hence, we develop an asynchronous distributed half‐duplex control protocol to regulate between the transmitting and receiving phases of transmissions. Furthermore, multi‐hop communications are very sensitive to the time variability of the received signal strength in the fading channel and the ambient noise dominated by snapping shrimp in harsh underwater environments, because a broken link in the multi‐hop path is enough to disrupt communications and initiate new route searches. In our configuration, we use the Ad hoc On‐demand Distance Vector (AODV) routing protocol optimized for UWA networks. Empirical studies show that we can model the channel as a slow‐varying frequency non‐selective Rayleigh fading channel. We theoretically analyze the throughput of our configuration by considering three salient features: the ability of the receiver to demodulate the data, the effect of our control protocol and the effect of disconnections on the generation of routing packets. The throughput under various operating conditions is then examined. It is observed that at optimal node separation, the throughput is improved by a factor of 10. Copyright © 2007 John Wiley & Sons, Ltd.

SNR analysis for multi-rate UWB-IR

This letter is motivated by the need to design MAC protocols for impulse radio ultrawide bandwidth systems. It evaluates the signal-to-noise ratio (SNR) in such multi-rate systems in which the different users transmit with different rates and different power levels. The SNR is obtained for all combinations of pulse-position modulation or pulse-amplitude modulation, with time-hopping and/or direct-sequence spreading. We show that the SNR in a multi-rate time-hopping system is different from a single-rate system, and is highly affected by the low-rate users

Cross-layer issues in MAC protocol design for MIMO ad hoc networks

In this article, we discuss research and design issues that arise in the development of networking protocols for an ad hoc network where nodes are equipped with multiple antenna elements and have the ability to perform signal processing operations as required by adaptive beamforming, interference cancellation, and space-time coding

A new approach to the design of MAC protocols for wireless LANs: combining QoS guarantee with power saving

An alternative WLAN protocol which could be adapted in the HCF access scheme defined by IEEE 802.11e, in place of the HCCA mechanism, is introduced. LEPOAC-QG (low energy priority oriented adaptive control with QoS guarantee) is a centralized access mechanism that supports low energy consumption, guarantees QoS for all types of multimedia network applications, enhances the parameterized traffic with priorities, and supports time division access. It instantly negotiates the quality levels of the traffic streams trying to support multiple streams with best possible quality. LEPOAC-QG, compared with HCCA, exhibits generally superior performance.

A new approach to the design of MAC protocols for wireless LANs: combining QoS guarantee with power saving

An alternative WLAN protocol which could be adapted in the HCF access scheme defined by IEEE 802.11e, in place of the HCCA mechanism, is introduced. LEPOAC-QG (low energy priority oriented adaptive control with QoS guarantee) is a centralized access mechanism that supports low energy consumption, guarantees QoS for all types of multimedia network applications, enhances the parameterized traffic with priorities, and supports time division access. It instantly negotiates the quality levels of the traffic streams trying to support multiple streams with best possible quality. LEPOAC-QG, compared with HCCA, exhibits generally superior performance.

A wireless MAC protocol using implicit pipelining

In distributed multiple access control protocols, two categories of overhead are usually associated with contention resolution. One is channel idle overhead, where all contending stations are waiting to transmit. Another is collision overhead, which occurs when multiple contending stations attempt to transmit simultaneously. Either idle overhead or collision overhead being large, contention resolution algorithm would be inefficient. Prior research work tries to minimize both the idle and the collision overheads using various methods. In this paper, we propose to apply "pipelining" techniques to the design of multiple access control protocol so that channel idle overhead could be (partially) hidden and the collision overhead could be reduced. While the concept of pipelined scheduling can be applied to various MAC protocol designs in general, in this paper, we focus on its application to IEEE 802.11 DCF. In particular, an implicitly pipelined dual-stage contention resolution MAC protocol (named DSCR) is proposed. With IEEE 802.11, the efficiency of contention resolution degrades dramatically with the increasing load due to high probability of collision. Using the implicit pipelining technique, DSCR hides the majority of channel idle time and reduces the collision probability, hence, improves channel utilization, average access delay, and access energy cost over 802.11 significantly both in wireless LANs and in multihop networks. The simulation results, as well as some analysis, are presented to demonstrate the effectiveness of DSCR.

On Profitability and Efficiency of Wireless Mesh Networks

The convenience of wireless networking and lightweight handheld devices has led to a large-scale adoption of wireless technologies. Corporations, universities, hospitals, homes, and public places are deploying these networks at a remarkable rate. In a wireless mesh network, a few Internet transmit access points (ITAPs), serving as gateways to the Internet, are deployed across the neighborhood. Wireless nodes (e.g., houses) are equipped with low-cost antennas, and serve as routers to send traffic for both itself and its neighbors. In this way, a multihop wireless network is formed among wireless nodes to cooperatively route traffic to the Internet through the ITAPs. Such a multihop structure dramatically reduces the number of ITAPs, which is a major cost in deployment. The promise of wireless mesh networks has attracted lots of research work in the area, ranging from designing MAC protocols to developing routing protocols and routing metrics, to studying interactions with TCP, to controlling topology via power control, channel assignment, and directional antennas. In addition to network technologies, another major factor that determines the success of wireless mesh networks is whether there exist viable business models. There is limited research on this problem. In wireless mesh networks, wireless nodes are required to forward traffic for both itself and its neighbors. If the nodes are controlled by self-interested users, they may not efficiently share their capacity to route traffic for other nodes. Such possibility undermines the performance and feasibility of wireless mesh networks. Therefore effective pricing mechanisms need to be developed before the mesh technologies are commercialized. Motivated by the observations, we develop two pricing mechanisms for non-cooperative wireless mesh networks: a centralized pricing mechanism and a decentralized one. In the centralized pricing mechanism, the service provider needs to monitor and price the traffic originated from every node, while the decentralized scheme leaves the traffic monitoring and pricing to each router. We describe algorithms a service provider uses to efficiently place the ITAPs, and determine the prices. We evaluate the profitability and overall efficiency of the wireless mesh network under the centralized and decentralized pricing mechanisms. As a comparison, we also analyze an alternative structure based on a single-hop wireless network. In such a network, each user can directly communicate with an ITAP, and does not rely on other users for its communication. On the other hand, the singlehop wireless network requires more Internet access points to be deployed, thereby increasing the infrastructure cost. Our analysis has important practical implications to wireless service providers and the future of wireless mesh technologies.

Design of an effective loss-distinguishable MAC protocol for 802.11 WLAN

In the IEEE 802.11 WLAN standard, the backoff algorithm assumes that all losses are due to collisions, while the automatic rate fallback algorithm assumes that all losses are due to link errors. The coexistence of these two types of losses in real networks reduces the efficiency of currently used algorithms. We propose a loss-distinguishable MAC layer protocol for 802.11 WLAN. No PHY layer modification is needed. Analysis shows that the new protocol is effective and has negligible overhead.

A new MAC protocol design based on TDMA/FDD for QoS support in WATM networks

Several wireless networking solutions have been developed to provide different types of services for various end user applications. Currently, wireless networking infrastructures are not suitable for multimedia applications each requiring a different QoS support with various traffic parameters. Due to the success of ATM technology in the wired network, WATM concept and related researches are of importance in the information technology area. Main objective of WATM, which promises seamless transmission of different traffics such as voice, data and video over wireless medium, is to implement high bit rate and QoS guaranteed data transfer, already well achieved by ATM technology over wired medium. To support QoS guaranteed data transfer over error-prone and low bandwidth wireless medium, an effective MAC protocol must be designed and utilized. In this paper, a new TDMA/FDD based MAC protocol, maintaining QoS requirements of real-time wireless multimedia applications, is proposed. The main contribution of this study is the new guarantee-based scheduling algorithm used in the proposed MAC to support required level of QoS guarantee for all multimedia traffic types in wireless medium. Computer modeling and simulation of the new approach providing CBR, VBR, ABR and UBR ATM services are realized using OPNET Modeler. Simulation results are also presented together with comparisons those of a WATM counterpart which uses PRMA/DA MAC protocol.

Optical storage area networks

Storage area networks (SANs) are a promising technology to efficiently manage the ever-increasing amount of business data. Extending SANs over large distances becomes essential to facilitate data protection and sharing storage resources over large geographic distances. A WDM metropolitan ring network is examined as a suitable extension for SANs where it is shown that sectioning the ring can help deal with traffic asymmetry and hot node (SAN node on ring) scenarios. Several network architectures are studied: One of the architectures accommodates a single SAN and its mirror connected through a sectioning link. Another architecture accommodates two pairs of SANs and their mirrors with sectioning links connecting each pair. Issues investigated include impact of the number of co-existing IP (non SAN) nodes; traffic models: Poisson and self-similar; slotted regime: fixed-size (FS), variable-size (VS) and supersize (SS) slot schemes; MAC protocol design; handling traffic asymmetry and performance measures.

An efficient polling and information-request packet transfer for wireless networks in fading and interference environments

The design of an efficient MAC protocol is of paramount interest for the definition of wireless ATM (WATM) access. Polling schemes of MAC layer protocol yields reasonably low link channel utilization efficiency and more delay when only small number of mobile stations have packets to transmit. This problem arises from the fact that all the remote units should be polled to know whether remotes have packet to transmit. This paper proposes an efficient algorithm for polling all the remotes currently under base station and bandwidth allocation for information-request packet transfer from remote-to-base direction in MAC layer protocol when only small number of remote unit (mobile station) awaiting to transmit packets. The mathematical and simulation results show that using proposed technique for slot allocation for information-request packet transfer the MAC overcomes the above inefficiency considerably yielding greater channel utilization efficiency and low delay.

Link-level measurements from an 802.11b mesh network

This paper analyzes the causes of packet loss in a 38-node urban multi-hop 802.11b network. The patterns and causes of loss are important in the design of routing and error-correction protocols, as well as in network planning.The paper makes the following observations. The distribution of inter-node loss rates is relatively uniform over the whole range of loss rates; there is no clear threshold separating "in range" and "out of range." Most links have relatively stable loss rates from one second to the next, though a small minority have very bursty losses at that time scale. Signal-to-noise ratio and distance have little predictive value for loss rate. The large number of links with intermediate loss rates is probably due to multi-path fading rather than attenuation or interference.The phenomena discussed here are all well-known. The contributions of this paper are an understanding of their relative importance, of how they interact, and of the implications for MAC and routing protocol design.

A predictive demand assignment multiple access protocol for Internet access over broadband satellite networks

AbstractMedium access control (MAC) protocol is responsible for wireless resource management, which is crucial to satellite communication. To enhance the performance of broadband satellite networks, the application characteristics should be considered in the design of the MAC protocol. With the rapid expansion of Internet applications and the attractiveness of high speed Internet access via broadband satellite networks, it becomes an attractive objective to take into account the self‐similar nature of Internet traffic in MAC protocol designs. This paper presents a novel predictive demand assignment multiple access (PRDAMA) protocol for packet communications over broadband satellite networks. PRDAMA allocates free bandwidth resources by estimating the positive varying trend of the Internet traffic to facilitate prediction of the bandwidth requirements of the earth stations. Simulation results demonstrate that PRDAMA achieves a lower average delay and delay jitter compared with other DAMA protocols under highly bursty traffic due to its accurate traffic trend prediction. With less bursty traffic, PRDAMA still performs better than the other DAMA protocols under a heavy traffic load. Copyright © 2003 John Wiley & Sons, Ltd.

Polling- and contention-based schemes for TDMA-TDD access to wireless ATM networks

The design of an efficient MAC protocol is of paramount interest for the definition of a wireless ATM (WATM) access. In the case of TDMA-TDD WATM access, the current trend in the standardization bodies is to adopt frames of fixed duration, whose slots are shared among uplink and downlink connections under the control of a MAC scheduler located in the base station. In this paper, we first compare polling and contention techniques, in order to identify the best access scheme to serve ATM connections. Then, since the knowledge of the queue status of the portable terminals can be used by the centralized scheduler to increase the efficiency of the slot assignment procedure, we propose different algorithms to code the buffer occupancy status. Moreover, we compare their performance by considering two different scenarios; the first loaded with ON-OFF sources served by nrt-VBR ATM connections, and the second with TCP/IP sources served by UBR ATM connections. The results show the superiority of the contention access and the advantages of the buffer status notification for the scheduler at the base station.

Stream traffic management over an ATM passive optical network

Several alternatives based either on wired or wireless infrastructures are considered for the provision of broadband services in the local loop. In the field of wired solutions, Passive Optical Networks (PON) look very promising due to their bandwidth capacity. Also called APONs (ATM over PON), PON systems are designed in order to satisfy end-to-end ATM connections. Because it is based on a point-to-multipoint optical tree configuration, a PON access system requires a MAC protocol for the upstream traffic. Two approaches may be adopted for the design of an APON MAC protocol. The first approach considers a MAC protocol based on a work-conserving discipline combined with a stand-alone traffic shaper between the head of the optical tree and an ATM switch. The second approach consists in an integrated mechanism able to reduce Cell Delay Variation (CDV) of CBR/VBR connections by means of non-work conserving disciplines at the MAC layer. After having described the main characteristics of APON systems, we propose a new APON MAC protocol with integrated shaping well suited to real time traffic management. The performances of our protocol are investigated by means of both computer simulations and analytical modeling. By extension of our analytical study, a Call Admission Control procedure is proposed for real time VBR connections.

A dynamic control scheme for the IEEE 802.14 draft MAC protocol over CATV/HFC networks

We first describe the draft multiple/random access protocol for IEEE 802.14 over the cable TV/hybrid fiber coaxial (CATV/HFC) networks. To best fit this draft protocol into the target network, we propose a dynamic control scheme to adequately adjust the parameters. Simulations of the draft protocol are then presented to depict the effectiveness of the proposed scheme and further highlight the directions for the design of MAC protocols over the CATV/HFC networks.