The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Existing contention based nonpersistent medium access control protocols in Wireless Sensor Network (WSN) do not perform well in high contention. Their performances are affected by occurrence of collision due to uniform probability distribution in choosing Time Slot (TS) during backoff period. To address this issue nonuniform probability distribution was proposed. However success rate still drops for...
The time-probability characteristics of the Associative Switching Fabric (ASF) are analyzed. A bipolar single-channel queuing system's stochastic model is regarded. For this model the Laplace-Stieltjes' transformation method is applied. The model is determined by two time allocation functions: the waiting function and the queuing function. The time-probability characteristics of timely delivery Q...
In this paper, we propose and analyze a TS (Tabu Search) algorithm for DSA (Dynamic Spectrum Access) in cellular networks. We consider a scenario where cellular operators share a common access band, and we focus on the strategy of one operator providing packet services to the end-users. We consider a soft interference requirement for the algorithm's design that suits the packet traffic context. The...
With the rapid development of network technology, computer network evolved to the mobile wireless Internet gradually, and showing a highly heterogeneous trend. The traditional TCP protocol is designed for wire circumstance and is obviously poor in such circumstance. This paper proposes a new TCP scheme, called TCP-C, which is based on Explicit Congestion Notification algorithm ( ECN), referencing...
This paper proposes an analytical model for the throughput of the Enhanced Distributed Channel Access (EDCA)mechanism in IEEE 802.11p MAC sub-layer. Features in EDCA such as different Contention Windows (CW) and Arbitration Interframe Space (AIFS) for each Access Category (AC), and internal collisions are taken into account. The analytical model is suitable for both basic access and the Request-To-Send/Clear-To-Send...
This paper proposes a differential codebook-based method to reduce the feedback overhead for closed-loop MIMO-OFDM systems. With the assumed multimode transmit precoding, both the number of data streams (rank) and the index of precoding matrix are fed back to the transmitter at each sub-band. By exploiting the channel correlation in frequency domain, an enhanced differential codebook (a subset of...
Coexistence between networks is an emerging challenge in the 60 GHz unlicensed band. An approximate analytical formulation of the saturated throughput of a cognitive IEEE 802.15.3c MAC in the directional contention access period (D-CAP) in the presence of contention time allocation period (CTAP) is presented in this paper. The analytical framework is formulated for N devices, including the pico-net...
Cooperative communications achieve tremendous improvements in system performance. Meanwhile, it tends to change the conventional access and transmission schemes in wireless networks. Thus, CoopMAC is proposed and analyzed for fully connected WLANs. It improves the performance of the network dramatically by enabling additional collaboration from other nodes. However, how does it work in multi-hop Ad...
In this paper, we consider the problem of power level selections under an average power constraint in slotted ALOHA networks. In the network, each node chooses a power level from a pre-determined power level set based on a probability for each access attempt. The derivation of the probability for maximizing the throughput is difficult. In addition, nodes may not always obey the given algorithm in...
A Hybrid ARQ (HARQ) scheme employing a flexible amplify and forward (AF) relaying is considered for a cooperative relay channel. Two phase types with flexible length: one phase for relay reception and another phase for relay forwarding are assumed to accommodate half duplex relaying. We assume two types of encoding: repetition coding (RC) and unconstrained coding (UC). The outage performance of the...
In this paper, a new joint scheduling and hybrid resource allocation method is derived and investigated for a multi-user downlink Orthogonal Frequency Division Multiple Access (OFDMA) system that provides Time Delay-Sensitive services (TDS) and Time Delay-Insensitive services (TDI). A three sectored multi-cellular heterogeneous traffic environment is considered where users are randomly distributed...
Channel reservation is used to decrease the drop ratio of secondary users caused by spectrum handover. This paper considers the maintainer of the reserved channels in one secondary system coexisting with multiple primary systems. The global channel reservation scheme, the user channel reservation scheme, and the user-updated channel reservation scheme are proposed, derived by different Markov models...
In this letter, the voice over IP (VoIP) capacity in Cognitive Radio system is studied with single and multiple channels. A special Cognitive Radio (CR) system is used, the Cognitive radio system adopt the frequency of near 700 M Hz, a wireless channel can be modeled as a two-dimensional discrete-time Markov chain. The traffic of a single VoIP user is described as a Markov modulated Poison process...
We consider a Decoded-and-Forward (DF) cooperative relaying network without a direct link. We investigate the outage probability (OP) of cooperation systems with either a DF scheme or a Selective DF (S-DF) scheme when relay channels experience statistically different Rayleigh fading. In the case of the DF system, an upper and lower bound of the OP are established to show the asymptotic performance...
In wireless multi-hop Ad hoc networks, contending existing at MAC layer could easily results in congestion, and the first-in-first-out queue within the nodes could make the head of the queue blocked, which affects the transmitting of the following packets. In this paper, we present a variable packet size supporting and congestion-based opportunistic packet scheduling (VS-CBOS) algorithm, in which...
This paper proposes a novel four-dimensional Markov chain model to evaluate performance of the Request To Send/Clear To Send (RTS/CTS) scheme of the IEEE 802.11 MAC protocol in multihop ad hoc networks. This model considers collision probability of the RTS frame and more important that of the Data frame after a successful RTS transmission. According to the division principle, network performance parameters,...
In this paper, we investigate the performance of a reuse partitioning (RUP) based cellular uplink system in a multicell environment. In a RUP scheme, a cell is divided into several concentric regions and each region has a different reuse factor. The model presented in this paper accounts for channel selection of a mobile station (MS) using a two-dimensional Markov, and co-channel interference (CCI)...
In order to improve the scheduling efficiency of IEEE 802.16 mesh mode, exactly theoretical analysis is necessary. In the IEEE 802.16 mesh mode with distributed coordinated scheduling, all nodes are peers and multi-hop communication is allowed. Every node has to compete for transmission opportunities based on scheduling information in the two-hop neighborhood. In this paper, we use probability-based...
The innovative exploitation of network coding technology could bring great design advantages to MANETs. First, wireless links are inherently lossy due to channel fading or interference. Second, the delivery condition of the route from the source to each receiver in a multicast transmission might be significantly distinct. Trying to satisfy the reliability requirement for the poorly-connected receivers...
We study the effect of relay cluster selection on throughout in multi-hop cooperative communications with one source and one destination. We evaluate the effective relay throughput as a function of the source transmission rate and the network outage probability. Assuming channel side information (CSI) only available at the receivers, we formulate the cluster size optimization to maximize throughput...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.