Design and analysis of random multiple access quantum key distribution

This article proposes a potential application of quantum key distribution in multiuser networks. In modern networks, variety of multiple access technologies are used for multiuser access purposes. In this article, we focus on a type of widely used media access control protocol - carrier-sense multiple access (CSMA) and analyze the use of carrier-sense multiple access with collision avoidance (CSMA/CA) for the quantum key distribution in the network. The quantum key generation is based on a successful experiment that implemented the quantum key distribution by using the decoy-state method. The secret key generation rate as the main indicator of the performance is given, including the relationship between it and the number of stations in the network, and the relationship between the key generation rate and the transmission distance under the multiple access condition as well. In addition, a multiple access quantum key distribution with channel detection protocol is also proposed

Study on Additional Carrier Sensing for IEEE 802.15.4 Wireless Sensor Networks

Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the guise of low-rate and short-distance wireless personal area networks (WPANs). The slotted carrier sense multiple access with collision avoidance (CSMA/CA) is used for contention mechanism. Sensor nodes perform a backoff process as soon as the clear channel assessment (CCA) detects a busy channel. In doing so they may neglect the implicit information of the failed CCA detection and further cause the redundant sensing. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. This paper proposes an additional carrier sensing (ACS) algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanism for the original slotted CSMA/CA. An analytical Markov chain model is developed to evaluate the performance of the ACS algorithm. Both analytical and simulation results show that the proposed algorithm performs better than IEEE 802.15.4, which in turn significantly improves throughput, average medium access control (MAC) delay and power consumption of CCA detection

Evaluation of Interference-Cancellation Based MAC Protocols for Vehicular Communications

Vehicular communications form an important part of future intelligent transport systems. Wireless connectivity between vehicles can enhance safety in vehicular networks and enable new services such as adaptive traffic control, collision detection and avoidance. As several new algorithms are being developed for enhancing vehicle to vehicle wireless connectivity, it is important to validate the performance of these algorithms using reasonably accurate wireless channel models. Specifically, some recent developments in the medium access control (MAC) layer algorithms appear to have the potential to improve the performance of vehicle to vehicle communications; however, these algorithms have not been validated with realistic channel models encountered in vehicular communications. The aforementioned issues are addressed in this thesis and correspondingly, there are two main contributions - (i) A complete IEEE 802.11p based transceiver model has been simulated in MATLAB and its performance & reliability are tested using existing empirically-developed wireless channel models. (ii) A new MAC layer algorithm based on slotted ALOHA with successive interference cancellation(SIC) has been evaluated and tested by taking into consideration the performance of underlying physical layer. The performance of slotted ALOHA-SIC and the already existing carrier sense multiple access with collision avoidance (CSMA/CA) scheme with respect to channel access delay and average packet loss ratio is also studied

Decentralized detection in IEEE 802.15.4 wireless sensor networks

We present a mathematical model to study decentralized detection in clustered wireless sensor networks (WSNs). Sensors and fusion centers (FCs) are distributed with the aim of detecting an event of interest. Sensors are organized in clusters, with FCs acting as cluster heads, and are supposed to observe the same common binary phenomenon. A query-based application is accounted for; FCs periodically send queries and wait for replies coming from sensors. After reception of data, FCs perform data fusion with a majority-like fusion rule and send their decisions to an access point (AP), where a final data fusion is carried out and an estimate of the phenomenon is obtained. We assume that sensors are IEEE 802.15.4-compliant devices and use the medium access control (MAC) protocol defined by the standard, based on carrier-sense multiple access with collision avoidance. Decentralized detection and MAC issues are jointly investigated through analytical modelling. The proposed framework allows the derivation of the probability of decision error at the AP, when accounting for packets' losses due to possible collisions. Our results show that MAC losses strongly affect system performance. The impact of different clustering configurations and of noisy communications is also investigated

Performance Analysis of Link Adaptive 802.11 WLANs with Multiuser Detection Capable Receivers

Conventional IEEE 802.11 Medium Access Control (MAC) protocol does not allow simultaneous transmissions from stations at any moment, to avoid collisions. Namely, it employs measures such as carrier sense multiple access, collision avoidance, and distributed coordination function which are designed to discourage simultaneous transmissions. With the advent of sophisticated physical layer technologies, multi-user detection capable receivers become available. In this paper, therefore, we aim to investigate if the popular 802.11 MAC can be modified to exploit this innovation in the physical layer. We accomplish this by deriving a new throughput expression. Modern WLANs support multiple data rate transmissions via link adaptation for higher spectral efficiency. Thus, we include multi rate link adaptation in the analysis. We find that 802.11 can be modified slightly to support simultaneous transmissions and to obtain significant benefit from multi-user detection capable receivers

Modeling Hidden Nodes Collisions in Wireless Sensor Networks: Analysis Approach

This paper studied both types of collisions. In this paper, we show that advocated solutions for coping with hidden node collisions are unsuitable for sensor networks. We model both types of collisions and derive closed-form formula giving the probability of hidden and visible node collisions. To reduce these collisions, we propose two solutions. The first one based on tuning the carrier sense threshold saves a substantial amount of collisions by reducing the number of hidden nodes. The second one based on adjusting the contention window size is complementary to the first one. It reduces the probability of overlapping transmissions, which reduces both collisions due to hidden and visible nodes. We validate and evaluate the performance of these solutions through simulations