In the 802.11 protocol, fundamental medium access mechanism is called Distributed Coordination Function (DCF). DCF, before making any transmission attempt, nodes count down a timer with value randomly selected from Contention Window (CW) size. If transmitted packet involved in collision, node increases CW size an attempt to reduce collision rate. Conversely, if successfully, reduces order incre...

En el presente trabajo se realizó un estudio voltamperométrico del proceso de redox diclofenaco (DCF) en medio acuoso a partir baño electrolítico composición 0.001 M DCF y 0.1 Na2SO4 pH= 7, sobre electrodo fibra carbono 7 mm diámetro. Los procesos oxidación relacionaron al su forma aniónica (DCF-A), mientras que los reducción par ion {DFC-A − Na+}0. Las tendencias lineales la corriente pico vs ...

Immune function in patients with hairy cell leukemia (HCL) was examined serially during treatment with alternating monthly cycles of recombinant interferon alpha-2a and 2'-deoxycoformycin (dCF). At presentation, most patients had normal numbers of T lymphocytes and their cells had normal proliferative responses to mitogens [phytohemagglutinin (PHA) and concanavalin A (Con A)] and alloantigens. ...

A two-screen sampler (an effective dosimeter), with a collection efficiency matched to the particle size response of the radon progeny dose conversion factors (DCF), obtained from the ICRP respiratory tract model as implemented in the computer code RADEP, has been developed to assess the inhalation dose from exposure to radon progeny. In order to evaluate the performance of this sampler, the se...

This paper investigates saturation and finite load throughputs of distributed coordinated function (DCF) as specified IEEE 802.11 wireless local area network (WLAN) protocol in presence of hidden stations. To study throughput of IEEE DCF, we extend Tobagi and Kleinrock’s hidden terminal model [1] and incorporate it into Bianchi’s Markov model of DCF [2]. We use the latter model to derive a gene...

Carrier sensing is widely adopted in wireless communication to protect data transfers from collisions. For example, distributed coordination function (DCF) in IEEE 802.11 standard renders a node to defer its communication if it senses the medium busy. For the duration of deferment, each frame carries, in its MAC header, a 16-bit number in microseconds during which any overhearing node must defe...

Being a part of IEEE project 802, the 802.11 Medium Access Control(MAC) is used to support asynchronous and time bounded delivery of radio data packets. It is proposed that a Distributed Coordination Function(DCF), which uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and binary slotted exponential backoff, be the basis of the IEEE 802.11 WLAN MAC protocols. This paper pro...

Performance of IEEE 802.11 distributed coordination function (DCF) has been studied by several authors under steady-state conditions. Behavior of DCF under transient state conditions and its modeling is important for analyzing several scenarios, such as, initialization of nodes in a wireless ad hoc network. In this paper, we present a mathematical model for IEEE 802.11 DCF to capture its behavi...

IEEE 802.11 has employed distributed coordination function (DCF) adopting carrier sense multiple access with collision avoidance (CSMA/CA). To effectively resolve collisions, DCF uses binary exponential backoff (BEB) algorithm with three parameters, i.e., backoff stage, backoff counter and contention window. If a collision occurs, stations involving in the collision increase their backoff stage...

Most of analytical models proposed so far for the IEEE 802.11 distributed coordination function (DCF) focus on saturation performance. In this paper, we develop an analytic model for unsaturation performance evaluation of the IEEE 802.11 DCF with and without slow contention window decrease (SCWD). The model explicitly takes into account the carrier sensing mechanism and an additional backoff in...