1,720,971 research outputs found
Bandwidth Allocation with Half-Duplex Stations in IEEE 802.16 Wireless Networks
No full textIEEE 802.16 is a recent IEEE standard for broadband wireless access networks. In IEEE 802.16 networks, the Medium Access Control ( MAC) protocol is centralized and explicitly supports quality of service ( QoS). That is to say, access to the medium by a number of Subscriber Stations ( SSs) is centrally controlled by one Base Station ( BS), which is responsible for allocating bandwidth to several MAC connections in order to provide them with the negotiated QoS guarantees. However, although the network can be operated in Frequency Division Duplex ( FDD) mode ( that is, transmissions from the BS ( downlink) and SSs ( uplink) occur on separate frequency channels), the standard supports SSs with half- duplex capabilities. This means that they are equipped with a single radio transceiver which can be used either to transmit in the uplink direction or to receive in the downlink direction. This may severely hamper the capacity to support QoS. Therefore, in order to allocate bandwidth, an IEEE 802.16 BS has to solve two related issues: 1) how it can schedule bandwidth grants to SSs in order to meet the QoS requirements of their connections and 2) how it can coordinate the uplink and downlink scheduled grants so as to support half- duplex capabilities. In this paper, we derive sufficient conditions for a set of scheduled grants to be allocated so that the transmission of each half- duplex SS does not overlap with its reception. Based on this, we propose a grant allocation algorithm, namely, the Half- Duplex Allocation ( HDA) algorithm, which always produces a feasible grant allocation provided that the sufficient conditions are met. HDA has a computation complexity of O(n), where n is the number of grants to be allocated. Finally, we show that the definition of HDA allows us to address the two issues mentioned above by following a pipeline approach. This is when scheduling and allocation are implemented by separate and independently running algorithms, which are just loosely coupled with each other. We show via extensive simulations that the performance of SSs with half- duplex capabilities, in terms of the delay of real- time and non- real- time interactive traffic, using HDA almost perfectly matches that of full- duplex SSs, whereas an alternative approach, based on the static partitioning of half- duplex SSs into separate groups, which are allocated alternately, is shown to degrade the performance
Scheduling, Routing, and Related Cross-Layer Management through Link Activation Procedures in Wireless Mesh Networks
No full textEnd-to-End Bandwidth Reservation in IEEE 802.16 Mesh Networks
No full textIEEE 802.16 mesh does not include support to traffic flows with strict Quality of Service requirements. In this paper, we propose an End-to-end Bandwidth Reservation Protocol (EBRP) in the backhaul of a Wireless Mesh Network using IEEE 802.16 mesh. The distinctive feature of EBRP is that it is carried out at the Medium Access Control (MAC) layer. Therefore, EBRP not only makes the resource reservation process extremely rapid, it also allows the available resources to be allocated efficiently by exploiting technology specific iinformation available at the MAC. We present EBRP as part of a framework which also includes the support for performing distributed Call Admission Control (CAC). Preliminary simulations results obtained
with VoIP traffic and nodes arranged in a grid topology are presented to show the effectiveness of EBRP, with ideal CAC computation
A general interference-aware framework for joint routing and link scheduling in wireless mesh networks
No full textJoint design and optimization of traditionally independent problems such as routing
and link scheduling have recently become one of the leading research trends in
wireless mesh networks. Although technically challenging, cross-layering is, in fact,
expected to bring significant benefits from the network resource exploitation standpoint
to achieve high system utilization. In this article we propose a versatile framework
for joint design of routing and link scheduling, introducing the notion of link
activation constraints, which are related to the transceiver capability and the
broadcast nature of the wireless medium. To this end, we introduce a taxonomy of
wireless interference models to harmonize existing approaches presented in the literature.
Finally, we evaluate the impact on network capacity of the various interference
models when optimal joint routing and link scheduling are employed
A general interference-aware framework for joint routing and link scheduling in wireless mesh networks
No full textJoint design and optimization of traditionally independent problems such as routing and link scheduling have recently become one of the leading research trends in wireless mesh networks. Although technically challenging, cross-layering is, in fact, expected to bring significant benefits from the network resource exploitation standpoint to achieve high system utilization. In this article we propose a versatile framework for joint design of routing and link scheduling, introducing the notion of link activation constraints, which are related to the transceiver capability and the broadcast nature of the wireless medium. To this end, we introduce a taxonomy of wireless interference models to harmonize existing approaches presented in the literature. Finally, we evaluate the impact on network capacity of the various interference models when optimal joint routing and link scheduling are employed
System and method for providing a fast and optimized uplink and downlink scheduling algorithm for use in FDD communication systems with half-duplex stations
No full textA system and method for scheduling uplink and downlink burst data transmissions for half-duplex terminals in a communication system. After the first half duplex terminal capacity allocation is scheduled for a plurality of half duplex terminals, all available second half duplex terminals are placed in the same relative order as that of the half duplex terminal first capacity allocation. An iterative process is used in order to determine a final second frame layout. Once a set of potential solutions are determined, one solution is selected, and a final second frame structure is determined
Scheduling, routing, and related cross-layer management through link activation procedures in wireless mesh networks,
No full textThis chapter describes scheduling, routing, and related cross-layer
management in Wireless Mesh Networks through the paradigm of link activatio
Pervasive video-surveillance systems over TCP/IP networks
No full textTraditional analog video surveillance systems technology has recently become inadequate to face the massive demand of security systems consisting of hundreds and sometimes thousands of cameras often deployed in hostile environments miles away from the control room. During the last few years, the rapid growth of the digital technology has produced sophisticated cameras which can directly record highdefinition digital videos. The packetized video stream can be straightforwardly conveyed to the control room, relaying on common IP network infrastructures. This solution result is extremely flexible as the network infrastructure can be built over a wide variety of heterogeneous network technologies from the traditional Ethernet-based Local Area Networks (LANs) to the recently proposed Wireless Mesh Networks (WMNs). However, the widespread adoption of IP-based solutions for video surveillance poses serious problems in terms of required bandwidth, processing power, network security, and system dependability. In this chapter, we first investigate the advantages of the IP-based video surveillance systems over the traditional analog ones. Then, we describe the technical challenges and the open research issues which still lack an ultimate solution which permits to completely abandon the traditional analog technology. Finally, we propose and verify, by means of a case study, a methodology to address the design of video surveillance systems in real deployment.</jats:p
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