A. Ferri

Bio: A. Ferri is an academic researcher from University of Florence. The author has contributed to research in topics: Network packet & Network congestion. The author has an hindex of 2, co-authored 3 publications receiving 20 citations.

A MAC technique for CDMA based ad-hoc networks

Abstract: Recently, ad-hoc networks have obtained a growing interest due to their advantages in many practical applications. One of the most critical points is the definition of an efficient medium access control (MAC) protocol that allows the transmission of packets generated by a node and routing of packets arriving from other nodes. This paper deals with a MAC technique based on code division multiple access (CDMA) scheme that adapts the used spreading factor to the network congestion in order to minimize the energy consumption and maximize the network throughput.

Medium access control protocol for CDMA ad hoc networks

Abstract: Recently, ad hoc networks have obtained a growing interest because of their advantages in many practical applications. One of the most critical points is the definition of an efficient medium access control (MAC) protocol that allows the transmission of packets generated by a node and routing of packets arriving from other nodes. A MAC technique is presented based on the code division multiple access (CDMA) scheme that adapts the used spreading factor to the network congestion in order to minimise the energy consumption and maximise the network throughput.

A novel MAC technique for ad-hoc CDMA networks

Abstract: In the recent years the high-speed data networking in a wireless infrastructure has became one of the most interesting topic both in industrial and research field. Among different standards and data rates one of the most important challenge in the future is established by the ad-hoc networks. They differs from the classical wireless local area networks (WLANs) for the absence of a coordinator device. In such networks the data exchange is autonomously routed by the devices that assume also the function of network nodes. One of the most interesting topics in wireless ad-hoc networks is the medium access control (MAC) protocol because each node have to sent packets generated by itself and route packets from other nodes; moreover, due to the absence of a coordination device, each node have to perform some algorithm in order to know which are the neighbor nodes. In this paper a MAC technique for code division multiple access (CDMA) networks is proposed, taking into account the adaptation of the spreading code in order to minimize the total network congestion.

Cross-layer designs of multichannel reservation MAC under Rayleigh fading

Abstract: We consider a reservation-based medium access control (MAC) scheme where users reserve data channels through a slotted-ALOHA procedure. The base station grants access to users in a Rayleigh fading environment using measurements at the physical layer and system information at the MAC layer. The paper has two contributions pertaining to simple reservation based medium access. First, we provide a Markov chain formulation to analyze the performance (throughput/channel utilization) of the multichannel slotted system. Second, a Neyman-Pearson like MAC design optimized for performance is presented. This design can serve as a benchmark in evaluating the performance of other designs based on conventional physical layer detectors such as maximum a posteriori probability, maximum likelihood, and uniformly most powerful detectors. Results show that utilizing system information in addition to the physical layer measurements indeed leads to a gain in performance. We discuss the issue of further improving the performance in fading by means of multiple measurements and also comment on the delay/channel-utilization trade-off for the optimal MAC design.

Connectivity of ad hoc wireless networks: an alternative to graph-theoretic approaches

Abstract: Connectivity in wireless ad hoc and sensor networks is typically analyzed using a graph-theoretic approach. In this paper, we investigate an alternative communication-theoretic approach for determining the minimum transmit power required for achieving connectivity. Our results show that, if there is significant multipath fading and/or multiple access interference in the network, then graph-theoretic approaches can substantially underestimate the minimum transmit power required for connectivity. This is due to the fact that graph-theoretic approaches do not take the route quality into consideration. Therefore, while in scenarios with line-of-sight (LOS) communications a graph-theoretic approach could be adequate for determining the minimum transmit power required for connectivity, in scenarios with strong multipath fading and/or multiple access interference a communication-theoretic approach could yield much more accurate results and, therefore, be preferable.

New CDMA-Based MAC Protocol for Ad Hoc Networks

Abstract: It is widely accepted that Ad Hoc networks are at the leading edge of the research in the domain of wireless networking. These networks are not supported by infrastructure to connect the mobile hosts, thereby they have to be self configured, self organized and the resources have to be allocated in a distributed manner. The medium access control (MAC) layer is seen as the bottleneck for the throughput in wireless Ad hoc networks. Hence, we propose in this work a new Multichannel MAC protocol. The proposed protocol can be based on Code Division Multiple Access (CDMA) or Frequency Division Multiple Access (FDMA). A channel can be represented by one spreading code in CDMA systems or by one frequency band in FDMA case. In our analysis and simulations, we assume that the protocol is based on CDMA technique. We consider one channel for control packets and multiple channels for transmitting data information. We propose that the reservation of a data cannel is done implicitly using the common channel. We show through computer simulations that our proposition of Multichannel MAC protocol improves significantly the communication performance in wireless Ad Hoc networks, even when the introduced overhead is considered.

Hybrid Dynamic Channel Assignment in Clustered Wireless Multihop CDMA/TDMA Ad Hoc Networks

Abstract: A good channel assignment scheme in a multihop ad hoc network should not only guarantee successful data transmissions without collisions, but also enhance the channel spatial reuse to maximize the system throughput. It becomes very inefficient to use fixed channel assignment when the network size grows. Therefore, spatial reuse of channels become more important in a large multihop ad hoc network. In this paper, we consider an ad hoc network with an overlaid CDMA/TDMA structure. We divide each code into time slots to form the channels. A dynamic channel assignment (DCA) strategy called Hybrid-DCA is proposed in a clustered ad hoc network. This DCA strategy is designed to make the best use of available channels by taking advantage of the spatial reuse concept. In Hybrid-DCA, the increase in spatial reuse is achieved by adding certain control overhead. We show that the bandwidth saving due to channel spatial reuse is higher than the additional bandwidth spent on the control overhead.

New Multichannel MAC Protocol for Ad Hoc Networks

Abstract: Since wireless ad hoc networks require a distributed multiple access protocol, the medium access control (MAC) layer can be seen as the bottleneck for the throughput in wireless 802.11-based ad hoc networks. In this paper, we develop a new MAC protocol for multichannel operation in wireless ad hoc networks. The proposed protocol is based on the code division multiple access (CDMA) technique where each spreading code represents one channel. However, the proposed MAC protocol is not limited to CDMA systems. It can be applicable within frequency division multiple access (FDMA) systems (with one radio transceiver) or multi radio systems. We show through computer simulations that our proposition of multichannel MAC protocol significantly improves the communication performance in wireless ad hoc networks.