QoS-aware cooperative medium access control for MIMO ad-hoc networks

To exploit multiuser diversity and achieve QoS requirements in MIMO ad hoc networks, we propose an optimal scheduling policy which utilizes stream control schemes. We also present a medium access control (MAC) protocol to implement the optimal scheduling policy. Simulation results show that our implementation achieves higher network throughput and provides better QoS support than the existing solutions.     

A MULTIPLE-RECEPTION ACCESS PROTOCOL WITH INTERRUPTIONS WITH MIXED PRIORITIES IN CDMA NETWORKS

A novel access protocol called Multiple-Reception Access Protocol (MRAP) and its modification MRAP/WI are proposed. In this protocol, all colliding users with a common code can be identified by the base station due to the offset of arrival time. Thus they can retransmit access requests under the base station‘s control. Furthermore new arrivals with higher priority level can interrupt the lower retransmission in order to reduce its access delay although it increases the lower priority‘s delay. Simulation results of MRAP and MRAP/WI are given in order to highlight the superior performance of the proposed approach.     

分组码分多址接入协议研究

本文提出一种用于语音／数据综合业务个人通信网的多址接入协议。该协议基于码分多址技术,分组预约方式,并采用了信道资源动态分配技术。其吞吐量,接入时延,呼损率等性能指标都得到了一定的提高。本文对协议性能进行了分析,并提出了计算机模拟认真的方法。     

Medium access protocol design for delay-guaranteed multicode CDMA multimedia networks

To enable multimedia real-time applications over next-generation wireless code-division multiple access (CDMA) packet-switching networks, previous efforts show a proper scheduling policy is the key to provide delay-guaranteed access services to various traffic types with different bit error rate (BER) requirements. Considering the support of the prevailing Internet protocol (IP) with variable-length packets in future mobile networks, we develop a mathematically delay-optimal medium access control (MAC) protocol over multicode CDMA (MC-CDMA) environments under the continuous-time assumption. From our investigations, we suggest that a good MAC protocol should be designed by using a proper single-server scheduling policy to guarantee packet-delay, and controlling the maximal number of simultaneous spreading-code transmissions to maintain the required BER. We further evaluate the performance of some MC-CDMA MAC protocols supporting QoS on BER and packet-delay, and show that MAC schemes conforming to our design rules give better performance on packet-delay when maintaining acceptable BER of various traffic types.     

A scalable distributed dynamic address allocation protocol for ad-hoc networks

Dynamic address allocation is an essential part in effective configuration and maintenance of a mobile ad-hoc network (MANET). In this paper, we present a new distributed dynamic address allocation protocol minimizing address allocation latency and communication overhead. Through analytic evaluation and experimental measurements, we show that scalability and faster recovery from failures can be achieved by dynamic address allocation. The dynamic address assignment protocol presented here requires a low memory footprint while supporting unicast, broadcast and multicast communication. A performance analysis of the proposed address allocation protocol is given in terms of address allocation latency and communication overhead. Node and Network mobility is addressed from the point of dynamic address management. The dynamic address allocation protocol is implemented on a TinyOS platform over a cluster tree network.     

A fair MAC protocol for resource sharing in ad-hoc cognitive networks

Cognitive Radio (CR) technology allows an opportunistic use of the licensed spectrum by the CR users, avoiding harmful interference to Primary Users (PUs). To perform their activity, secondary users (SUs) have particular features compared to the PUs; sensing is one of the principal. Specifically the CR users must detect the spectrum holes left by PUs by performing sensing. All the protocol stack need to be redesigned taking into account the specificity of the cognitive environment. In this paper a novel MAC protocol for cognitive radio wireless ad-hoc networks is presented and analysed. The introduced protocol is distributed, collision-free and guarantees a fair channel assignment, also taking into account the requests of Quality of Service (QoS) of the CR nodes. The performance of the protocol has been studied through statistical computations. In particular, a Markov chain has been introduced to study the global performance of the protocol. In addition a simulation tool has been developed to validate the mathematical model and to prove the fairness of the resource sharing mechanism. The results prove the protocol efficiency and the high fairness, measured with the help of the Jain’s fairness index.     

Mobility-aware timeout medium access control protocol for wireless sensor networks

Wireless sensor networks (WSNs), has been under development for a while by the academia and industry. Due to limited computational power, a typical sensor node may experience operational challenges. Moreover, mobility has become an important feature since emergency and healthcare related applications are evolving in WSNs. Consideration of mobile nodes in WSNs introduce new challenges for the designers. In this paper, an enhanced version of T-MAC protocol (a well-known medium access control protocol in WSNs) known as MT-MAC is proposed. Using the capturing fluctuation in RSSI and LQI values of the received SYNC packets, MT-MAC solves high packet drop ratio in T-MAC. By detecting the mobility, a mobile node softly handover to a new virtual cluster without losing connection with other nodes. The performance of the proposed solution is then compared with T-MAC, S-MAC as well as other well-known mobility-aware MAC (MS-MAC) protocol. The simulation results show that the proposed protocol significantly increases the throughput and packet delivery ratio of T-MAC in exchange for a small increase in power consumption. Compared to MS-MAC protocol, the proposed approach can reduce power consumption by 20–65%, and achieve slightly higher packet delivery ratio.     

WRAP: a medium access control protocol for wavelength-routedpassive optical networks

We describe the WDM request/allocation protocol (WRAP), a media-access control protocol for wavelength-routed passive optical networks (WR-PONs) in which each node has a single fixed optical receiver and a single tunable optical transmitter. The protocol does not require a carrier sensing capability, a separate control channel, or any centralized control or scheduling. Access to transmission channels is regulated by allocations made at destination nodes in response to requests made by source nodes. Computer simulation is used to investigate three different allocation algorithms, one of which-the preferential/random algorithm-is shown to provide significantly better performance than the alternatives. Simulations are presented comparing the performance of WRAP to two previously proposed applicable protocols-the interleaved time division multiple access (I-TDMA) protocol, and the FatMAC protocol. WRAP is shown to provide fair and flexible access to the transmission capacity, enabling high network utilization to be achieved under a wide range of traffic conditions, while providing a guaranteed minimum bandwidth between each source-destination pair. We conclude that of the three protocols considered here, WRAP is the best-suited to general-purpose data communications applications such as local, campus, and metropolitan area networks     

A schedule‐based medium access control protocol for mobile wireless sensor networks

Recent advances in body area network technologies such as radio frequency identification and ham radio, to name a few, have introduced a huge gap between the use of current wireless sensor network technologies and specific needs of some important wireless sensor network applications such as medical care, disaster relief, or emergency preparedness and response. In these types of applications, the mobility of nodes can occur, leading to the challenge of mobility handling. In this paper, we address this challenge by prioritizing transmissions of mobile nodes over static nodes. This is achieved by using shorter contention windows in reservation slots for mobile nodes (the so‐called backoff technique) combined with a novel hybrid medium access control (MAC) protocol (the so‐called versatile MAC). The proposed protocol advocates channel reuse for bandwidth efficiency and management purpose. Through extensive simulations, our protocol is compared with other MAC alternatives such as time division multiple access and IEEE 802.11 with request to send/clear to send exchange, chosen as benchmarks. The performance metrics used are bandwidth utilization, fairness of medium access, and energy consumption. The superiority of versatile MAC against the studied benchmark protocols is established with respect to these metrics. Copyright © 2012 John Wiley & Sons, Ltd.     

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division multiple access (TDMA) slot assignment protocol (ATSA) for vehicular ad-hoc networks. ATSA divides different sets of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks (VeMAC) and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.     

Information-centric dissemination protocol for safety information in vehicular ad-hoc networks

In vehicular networks, efficient safety information dissemination is a crucial issue. Unique characteristics of such an environment like highly mobility, fast topology changing, short-lived and intermittent connectivity pose challenges for safety information dissemination. Although IEEE 802.11p is standardized as an amendment to the IEEE 802.11 for connection-based wireless communication in vehicular environments (WAVE), it is still an open topic and a challenge to efficiently handle high mobility, intermittent connectivity, and spontaneous characteristics of vehicles on the roadway during wireless communication. This paper exploits information centric networking approach to design an efficient information dissemination protocol for such a challenging environment. The protocol is designed for both communication schemes in vehicular networks including vehicles-to-vehicles and vehicle-to-road. By focusing on information object itself, instead of end-to-end connection, the proposed mechanism supports fast and efficient data dissemination among multiple content consumers and multiple content providers, removing dependence on end-to-end connection between two nodes, thus improve the overall network performance. Through experimental results over different scenarios, we show that the proposed protocol achieves a significant improvement in term of the network performance compared to the conventional approach (WAVE).     

Agent-based trusted on-demand routing protocol for mobile ad-hoc networks

The routing performance in mobile ad hoc networks (MANETs) relies on the co-operation of the individual nodes that constitute the network. The existence of misbehaving nodes may paralyze the routing operation in MANETs. To overcome this behavior, the trustworthiness of the network nodes should be considered in the route selection process combined with the hop count. The trustworthiness is achieved by measuring the trust value for each node in the network. In this paper, a new protocol based on self monitoring (agent-based) and following the dynamic source routing (DSR) algorithm is presented. This protocol is called agent-based trusted dynamic source routing protocol for MANETs. The objective of this protocol is to manage trust information locally with minimal overhead in terms of extra messages and time delay. This objective is achieved through installing in each participated node in the network a multi-agent system (MAS). MAS consists of two types of agents: monitoring agent and routing agent. A new mathematical and more realistic objective model for measuring the trust value is introduced. This model is weighted by both number and size of routed packets to reflect the “selective forwarding” behavior of a node. The performance evaluation via simulation shows that our protocol is better than standard and trusted DSR. The simulation is done over a variety of environmental conditions such as number of malicious nodes, host density and movement rates.     

An adaptive low-overhead resource discovery protocol for mobile ad-hoc networks

In this paper we propose a Distributed Hash Table (DHT)-based peer-to-peer resource discovery protocol designed for large-scale Mobile Ad-hoc NETwork (MANET). The proposed Mobile Resource Discovery Protocol (MRDP) uses a distributed dynamic clustering algorithm to adaptively and rapidly group nodes in a MANET for resource discovery purpose, and utilizes DHTs to efficiently cache resource information in a peer-to-peer manner. We provide a probabilistic lower bound on the performance of the MRDP. We also present simulation results under different scenarios to show that MRDP has low message overheads and its performance is highly insensitive to the size of the MANET. These characteristics make MRDP suitable for large-scale MANETs.     

The role of optical CDMA in access networks

We investigate the possible role of optical CDMA (O-CDMA) in future access networks. We begin with a short review of the O-CDMA technique for those unfamiliar with the technology. Next, we investigate in detail those characteristics of O-CDMA that make it an attractive technology for application in metro access networks: fairness, flexibility, simplified network control and management, service differentiation, and increased security. Although O-CDMA has many favorable attributes, it also has several actual or perceived drawbacks. We discuss the technical, economic, and perception barriers that may have limited the widescale deployment of O-CDMA access networks. We try to determine which of these drawbacks may be surmountable in the near future and which may be true "showstoppers"     

SEAD: A simple and efficient adaptive data dissemination protocol in vehicular ad-hoc networks

Vehicular ad-hoc network (VANET) is becoming a promising technology for improving the efficiency and the safety of intelligent transportation systems by deploying a wide variety of applications. Smart vehicles are expected to continuously exchange a huge amount of data either through safety or non-safety messages dedicated for road safety or infotainment and passenger comfort applications, respectively. One of the main challenges posed by the study of VANET is the data dissemination design by which messages have to be efficiently disseminated in a high vehicular speed, intermittent connectivity, and highly dynamic topology. In particular, broadcast mechanism should guarantee fast and reliable data delivery within a limited wireless bandwidth in order to fit the real time applications’ requirements. In this work, we propose a simple and efficient adaptive data dissemination protocol called “SEAD”. On the one hand, the originality of this work lies in its simplicity and efficiency regardless the application’s type. Simplicity is achieved through a beaconless strategy adopted to take into account the surrounding vehicles’ density. Thanks to a metric locally measured, each vehicle is able to dynamically define an appropriate probability of rebroadcast to mitigate the broadcast storm problem. Efficiency is manifested by reducing excessive retransmitted messages and hence promoting the network capacity and the transmission delay. The simulation results show that the proposed protocol offers very low packet drop ratio and network load while still maintaining a low end-to-end delay and a high packet delivery. On the other hand, SEAD protocol presents a robust data dissemination mechanism which is suitable either for safety applications or for other kinds of application. This mechanism is able to adapt the protocol performance in terms of packet delivery ratio to the application’s requirements.     

A load awareness medium access control protocol for single‐hop wireless ad hoc networks

A contention‐based wireless ad hoc medium access control (MAC) protocol, such as carrier sense multiple access with collision avoidance (CSMA/CA), has excellent efficiency when the system is light loaded. The main drawback of such protocols is their inefficiency and unbounded delay when the system load is heavy. On the other hand, a contention‐free MAC protocol, such as token passing, has a better and fair throughput when the system is heavy loaded. The main drawback of such protocols is their inefficiency when only a small amount of users want to transmit. In this paper, we propose a new load awareness single‐hop wireless ad hoc MAC protocol (which is called the LA protocol) that exploits the benefits of both contention‐based and contention‐free protocols. A contention‐based MAC protocol is used when the system is light loaded and a contention‐free one is used otherwise. Our LA protocol, which operates in a distributed fashion and is fully compatible with the IEEE 802.11 wireless local area network (WLAN) standard, can switch smoothly between the contention‐based protocol and the contention‐free one. Simulation results show that our protocol indeed extracts the better part of two kinds of protocols. Copyright © 2006 John Wiley & Sons, Ltd.     

PEDAMACS: power efficient and delay aware medium access protocol for sensor networks

PEDAMACS is a Time Division Multiple Access (TDMA) scheme that extends the common single hop TDMA to a multihop sensor network, using a high-powered access point to synchronize the nodes and to schedule their transmissions and receptions. The protocol first enables the access point to gather topology (connectivity) information. A scheduling algorithm then determines when each node should transmit and receive data, and the access point announces the transmission schedule to the other nodes. The performance of PEDAMACS is compared to existing protocols based on simulations in TOSSIM, a simulation environment for TinyOS, the operating system for the Berkeley sensor nodes. For the traffic application we consider, the PEDAMACS network provides a lifetime of several years compared to several months and days based on random access schemes with and without sleep cycles, respectively, making sensor network technology economically viable.     

A cross-layer protocol for exploiting cooperative diversity in multi-hop wireless ad hoc networks

Cooperative communication has emerged to reap the benefits of spatial diversity. To fully exploit cooperative diversity, we propose a medium access control and routing enabled cross-layer cooperative transmission (MACR-CCT) protocol for improving the performance in multi-hop wireless ad hoc networks (MWAN). Different from previous cooperative protocols that determine a receiver in one hop according to a non-cooperative routing protocol first and then select a cooperative relay, MACR-CCT selects the cooperative relay together with the receiver in one hop to exploit fully cooperative diversity, so that the receiver is selected for higher cooperative gain and closer distance to destination, and the relay is selected to achieve the better throughput performance while considering transmission error. Furthermore, considering that there are multiple source–destination pairs in MWAN, MACR-CCT takes interference mitigation into account to further improve network throughput when selecting the cooperative relay. Besides, we propose a theoretical model to analyze the throughput performance. Finally, we take advantage of simulation results to validate the effectiveness of our analytical model and show that our proposed MACR-CCT protocol can significantly outperform existing packet transmission mechanisms in terms of throughput and delay under the multi-hop multi-flow network scenario.     

A new busy signal-based MAC protocol supporting QoS for ad-hoc networks with hidden nodes

This article presents three versions of a novel MAC protocol for IEEE 802.11 ad-hoc networks called Busy Signal-based Mechanism turned On (BusySiMOn) (This is an extended version of our conference paper: [15]). The key idea of the proposed solution is based on an intelligent two-step reservation procedure combined with the advantages of EDCA service differentiation. The former alleviates the hidden node problem while the latter ensures compatibility with the IEEE 802.11 standard. Simulation results obtained for saturated and non-saturated network conditions emphasize the advantages of the new protocol over the currently used four-way handshake mechanism in terms of fairness, throughput, and average frame delay.     

Adaptive digital access protocol: a MAC protocol for multiservicebroadband access networks

The authors describe a protocol that can adapt to the changing demands of a mix of synchronous transfer mode (STM) and asynchronous transfer mode (ATM) applications and efficiently allocate bandwidth to a variety of bursty traffic sources. In the case of a hybrid fiber-coaxial (HFC) network, the protocol resides in customer premises equipment (CPE) and a common head-end/central-office (HE/CO) controller. A medium-access control (MAC) processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable-length time slots are allocated to calls (e.g., telephony, video telephony) requiring different amounts of bandwidth. In the upstream channels, a contention access signaling time slot is also provided in the STM region for call control and setup requests. Within the ATM region, fixed-length time slots accommodate one individual ATM cell. These ATM time slots may be reserved for a user for either the duration of a call or a burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and setup requests. The MAC-layer protocol, its relation to circuit- and ATM-amenable applications, and its performance with respect to throughput, latency, and bandwidth efficiency for several service scenarios are examined