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Showing papers on "Timer published in 2010"


Proceedings ArticleDOI
01 Nov 2010
TL;DR: This work is the first to accurately infer, for any UMTS network, the state machine that guides the radio resource allocation policy through a light-weight probing scheme, and explores the optimal state machine settings in terms of several critical timer values evaluated using real network traces.
Abstract: 3G cellular data networks have recently witnessed explosive growth. In this work, we focus on UMTS, one of the most popular 3G mobile communication technologies. Our work is the first to accurately infer, for any UMTS network, the state machine (both transitions and timer values) that guides the radio resource allocation policy through a light-weight probing scheme. We systematically characterize the impact of operational state machine settings by analyzing traces collected from a commercial UMTS network, and pinpoint the inefficiencies caused by the interplay between smartphone applications and the state machine behavior. Besides basic characterizations, we explore the optimal state machine settings in terms of several critical timer values evaluated using real network traces. Our findings suggest that the fundamental limitation of the current state machine design is its static nature of treating all traffic according to the same inactivity timers, making it difficult to balance tradeoffs among radio resource usage efficiency, network management overhead, device radio energy consumption, and performance. To the best of our knowledge, our work is the first empirical study that employs real cellular traces to investigate the optimality of UMTS state machine configurations. Our analysis also demonstrates that traffic patterns impose significant impact on radio resource and energy consumption. In particular, We propose a simple improvement that reduces YouTube streaming energy by 80% by leveraging an existing feature called fast dormancy supported by the 3GPP specifications.

299 citations


Journal ArticleDOI
TL;DR: An integrated approach to tracking the end point of a time-based assay that is conducted on an analytical device made out of paper and fluidic timers, which provide slightly better accuracy than an external timer when used to track an assay that measured the level of glucose in a sample.
Abstract: This article describes an integrated approach to tracking the end point of a time-based assay that is conducted on an analytical device made out of paper The timing mechanism is built directly into a paper-based analytical device and does not require starting, stopping, reset buttons, batteries, or maintenance; the timer simply starts once the sample is added to the device These “fluidic timers” are composed of paraffin wax and a signaling feature (eg, a dye) The timing function is made possible by the specific time required for a liquid sample to wick through predefined regions in the device This time period can be anywhere between 1 min and 2 h and is controlled by the quantity of wax present in the timer Because both the fluidic timers and paper-based assays depend on the wicking rate of the sample, the fluidic timers automatically calibrate themselves (relative to the assay) to account for differences in wicking rates that are caused by variations in humidity Fluidic timers are 97% accurate (w

172 citations


Patent
02 Feb 2010
TL;DR: In this paper, the user equipment is configured to transmit scheduling requests to the base station only at certain predetermined scheduling request opportunities, and a corresponding method and arrangement in a base station is described.
Abstract: Method and arrangement in a user equipment for transmitting scheduling requests to a base station The base station is adapted to serve the user equipment The user equipment is configured to transmit scheduling requests to the base station only at certain predetermined scheduling request opportunities The method comprises triggering a scheduling request transmission, transmitting a scheduling request to the base station at the next occurring scheduling request opportunity, starting a scheduling request prohibiting timer and prohibiting any further scheduling request retransmission at future scheduling request opportunities while the scheduling request prohibiting timer is running Also, a corresponding method and arrangement in a base station is described

163 citations


Patent
28 Jan 2010
TL;DR: In this article, a method and apparatus for dual-carrier operation is described, where a first timer is initiated for an anchor carrier and a second timer for a supplementary carrier.
Abstract: A method and apparatus are described for performing a dual-carrier operation. A first timer is initiated for an anchor carrier and a second timer is initiated for a supplementary carrier. A physical channel failure may be declared on a condition that either of the timers expire before a predefined number of in-synch indication received from a layer 1 (L1) entity is counted. Uplink transmission and enhanced dedicated channel (E-DCH) operations may be stopped on a supplementary carrier associated with the physical channel failure, but may be continued on an anchor carrier that has a physical channel established. If the physical channel failure is associated with the anchor carrier, uplink transmission and E-DCH transmission operations are stopped on all carriers.

93 citations


Patent
27 Jul 2010
TL;DR: In this paper, a vital-signs patch for a patient monitoring system is disclosed, which consists of a housing that is configured to be worn on the skin of a patient.
Abstract: A vital-signs patch for a patient monitoring system is disclosed. The patch consists of a housing that is configured to be worn on the skin of a patient. The housing contains a radio, one or more sensor interfaces, a processor, and a battery. The processor can selectably turn portions of the processor off and on and selectably turn power off and on to at least a portion of the sensor interfaces and radio. The processor includes a timer that, each time the timer times out, will turn all the parts of the processor on and start a new timing period. When the processor receives a signal, the processor will turn off power to at least a portion of the processor and at least a portion of the sensor interfaces.

87 citations


Journal ArticleDOI
TL;DR: For any probability distribution function of the metric, the optimal scheme is scalable, distributed, and performs much better than the popular inverse metric timer mapping, and compares favorably with splitting-based selection, when the latter's feedback overhead is accounted for.
Abstract: Timer-based mechanisms are often used to help a given (sink) node select the best helper node from among many available nodes. In these, a node transmits a packet when its timer expires. The timer value is a monotone non-increasing function of its local suitability metric, which ensures that the best node is the first to transmit and is selected successfully if no other node's timer expires within a 'vulnerability' window after its timer expiry and so long as the sink can hear the available nodes. In this paper, we show that the optimal metric-to-timer mapping that (i) maximizes the probability of successful selection or (ii) minimizes the average selection time subject to a minimum constraint on the probability of success, maps the metric into a set of discrete timer values. We specify, in closed-form, the optimal scheme as a function of the maximum selection duration, the vulnerability window, and the number of nodes. An asymptotic characterization of the optimal scheme turns out to be elegant and insightful. For any probability distribution function of the metric, the optimal scheme is scalable, distributed, and performs much better than the popular inverse metric timer mapping. It even compares favorably with splitting-based selection, when the latter's feedback overhead is accounted for.

78 citations


Patent
23 Jun 2010
TL;DR: In this paper, an EVSE system includes an electric vehicle supply circuit, and a timer adapted to automatically control the circuit at one or more predetermined times, which can be coordinated with a scheduling system such as a calendar utility on a computer or portable communication device such as smart phone.
Abstract: An EVSE system includes an electric vehicle supply circuit, and a timer adapted to automatically control the electric vehicle supply circuit. The timer may be adapted to enable and/or disable the electric vehicle supply circuit at one or more predetermined times. The timer may be coordinated with a scheduling system such as a calendar utility on a computer or portable communication device such as a smart phone. The system may include a user interface for the timer. The user interface may include an embedded server such as an embedded web server to enable a user to program the timer through the Internet.

77 citations


Patent
27 Dec 2010
TL;DR: In this article, the authors propose to use expiration window timers, state-based timers and/or the coordination of keep-alive timers to reduce power consumption of mobile computing devices.
Abstract: Mobile computing device power consumption can be reduced by using expiration window timers, state-based timers and/or the coordination of keep-alive timers. Upon detecting a trigger event causing a mobile computing device to transition from a low-power state to an active state, the device can determine whether the trigger event occurs within the expiration window of a timer, and execute tasks associated with the trigger event and the timer. Tasks associated with state-based timers can be executed if the mobile computing device or a component thereof is in (or, alternatively, not in) a specified state. A mobile computing device can execute tasks associated with multiple keep-alive timers used for maintaining communication links between the device and cloud-based service providers in a single active state. A cloud-based keep-alive service can maintain mobile computing device-service provider communication links by sending one keep-alive communication to a mobile computing device in place of multiple communications.

76 citations


Journal ArticleDOI
TL;DR: In this paper, the authors explore the impact of the countdown timer at various stages of the signal cycle, using two approaches: a traffic analysis and a public opinion survey conducted in Bangkok.

67 citations


Patent
19 Mar 2010
TL;DR: In this paper, a power management method consisting of checking existence of a manufacturing identifier (ID) of a human interface device (HID) when the computer system is operated in a first mode, continuously detecting whether the HID exist when the manufacturing ID exists, starting a timer, entering a second mode when the timer expires, determining whether HID is operating in the second mode, when plugged into a computer system, and performing state transition on the computer systems when determining that the computer System is in second mode; and entering the first mode when detecting the state transition.
Abstract: A power management method is disclosed. The power management method comprises the step of a computer system checking existence of a manufacturing identifier (ID) of a human interface device (HID) when the computer system is operated in a first mode; the computer system continuously detecting whether the HID exist when the manufacturing ID exists; the computer system starting a timer when the computer system detects that the HID does not exist; the computer system entering a second mode when the timer expires; the HID determining whether the computer system is operated in the second mode, when plugged into the computer system; the HID performing state transition on the computer system when determining that the computer system is in the second mode; and the computer system entering the first mode when detecting the state transition.

64 citations


Patent
24 Sep 2010
TL;DR: In this paper, the authors propose a method and apparatus for virtual private network (VPN) liveness checking, the method, upon expiration of a timer, sending, over a VPN tunnel, a request to a server located behind a terminator of the VPN; checking whether a response to the request is received within a time interval, resetting the timer; and if a response is not received within an interval, resending the request if a request count is less than a set number of requests; or providing an inactive tunnel indication to a VPN client manager if the request count equals the set
Abstract: A method and apparatus for virtual private network (‘VPN’) liveness checking, the method, upon expiration of a timer, sending, over a VPN tunnel, a request to a server located behind a terminator of the VPN; checking whether a response to the request is received within a time interval; if a response to the request is received, resetting the timer; and if a response to the request is not received within the time interval, resending the request if a request count is less than a set number of requests; or providing an inactive tunnel indication to a VPN client manager if the request count equals the set number of requests.

Journal ArticleDOI
TL;DR: This paper introduces Circus Time, a timed extension of Circus, and presents a new UTP time theory, which is used to give semantics to Circus Time and to validate some of its laws, and provides a framework for validation of timed programs based on FDR, the CSP model-checker.
Abstract: Following the trend to combine techniques to cover several facets of the development of modern systems, an integration of Z and CSP, called Circus, has been proposed as a refinement language; its relational model, based on the unifying theories of programming (UTP), justifies refinement in the context of both Z and CSP. In this paper, we introduce Circus Time, a timed extension of Circus, and present a new UTP time theory, which we use to give semantics to Circus Time and to validate some of its laws. In addition, we provide a framework for validation of timed programs based on FDR, the CSP model-checker. In this technique, a syntactic transformation strategy is used to split a timed program into two parallel components: an untimed program that uses timer events, and a collection of timers. We show that, with the timer events, it is possible to reason about time properties in the untimed language, and so, using FDR. Soundness is established using a Galois connection between the untimed UTP theory of Circus (and CSP) and our time theory.

Patent
Mohit Kalra1
14 Oct 2010
TL;DR: A time-based breakpoint facility for debugging a program upon expiration of a timer is provided in this article, where the break exception is raised by a trigger or by a breakpoint.
Abstract: A time-based breakpoint facility is provided for debugging a program upon expiration of a timer. More particularly, encountering a break exception during an execution of a program results in determining if the break exception is raised by a trigger or by a breakpoint. If the break exception is raised by the trigger, steps include breaking the program execution, starting a timer and resuming the program execution without passing control to a user interface thread until the started timer expires. If the break exception is raised by the breakpoint, steps include breaking the program execution, passing control to the user interface thread, performing a debugging operation, and resuming the program execution upon indication of the user interface thread.

Patent
20 Dec 2010
TL;DR: In this article, a DC-DC converter includes a power switching device and a mode control logic circuit to control the power switching devices and generate an ON-pulse, and a flip-flop is configured to be set by the mode controller logic circuit.
Abstract: A DC-DC converter includes a power switching device and a mode control logic circuit to control the power switching device and generate an ON-pulse. A flip-flop is configured to be set by the mode control logic circuit. A current mode comparator is configured to reset the flip-flop and to compare a signal based upon current flowing through the power switching device with a signal based upon an output voltage of the dual mode flyback DC-DC converter. A transformer is driven by the current mode comparator. The mode control logic circuit includes a timer starting when a gate driver control signal applied to the power switching device turns the power switching device off and configured to generate a pulse when an off time interval elapses, a zero current detector circuit configured to sense a voltage on the transformer and generate a pulse when the voltage drops below a trigger threshold, and a combinatory logic circuit configured to compare pulse signals generated by the timer and the zero current detector circuit and generate the ON-pulse based thereupon.

Patent
07 May 2010
TL;DR: In this article, a processor/timer unit may be used to implement a power-managed lock acquisition mechanism, in which the processor is awakened a number of times to check the lock and execute the wait for event instruction if the lock is not free, after which the thread may block until the lock was free.
Abstract: In an embodiment, a timer unit may be provided that may be programmed to a selected time interval, or wakeup interval. A processor may execute a wait for event instruction, and enter a low power state for the thread that includes the instruction. The timer unit may signal a timer event at the expiration of the wakeup interval, and the processor may exit the low power state in response to the timer event. The thread may continue executing with the instruction following the wait for event instruction. In an embodiment, the processor/timer unit may be used to implement a power-managed lock acquisition mechanism, in which the processor is awakened a number of times to check the lock and execute the wait for event instruction if the lock is not free, after which the thread may block until the lock is free.

Journal ArticleDOI
TL;DR: In this paper, the authors designed and tested two ICs, powered solely through a connection to Bigleaf maple trees, which can be deployed to generate a usable voltage level for standard circuits.
Abstract: Complex patterns of electrical potential differences exist across the structure of a tree. We have characterized these voltages, and measured values ranging from a few millivolts to a few hundred millivolts for Bigleaf maple trees. These potential differences provide a unique opportunity to power nanoelectronic circuits directly from a tree. We have designed, constructed, and successfully tested two ICs, powered solely through a connection to Bigleaf maple trees. The first circuit, built in a 130-nm technology, creates a stable 1.1 V supply from input voltages as low as 20 mV, and can be deployed to generate a usable voltage level for standard circuits. The second circuit, fabricated in 90-nm technology is a timer, operating at 0.045 Hz and can be used for time keeping in stand-alone sensor network nodes. The boost circuit and timer consume 10 and 2.5 nW of power during operation, respectively.

Journal ArticleDOI
TL;DR: A novel model for stochastic analysis of timer-based power management in infrastructure IEEE 802.11 WLANs is developed and results enable an efficient power management algorithm that optimizes the idle timer and doze duration at the STA and the frame buffer at the access point.
Abstract: To achieve a long run-time for battery-operated portable electronic devices that incorporate wireless transceivers, efficient power management of the radio is a critical requirement. The power management function of IEEE 802.11 wireless local area networks (WLANs) allows stations (STAs) to operate in the doze mode so that their power consumption is significantly reduced. Hence, efficient algorithms to manage when and how often a STA enters and exits doze mode are crucial to battery-operated STAs. We address this problem by developing a novel model for stochastic analysis of timer-based power management in infrastructure IEEE 802.11 WLANs. Based on this model, the probabilities that a STA is active, idle, or dozing are derived, and the power consumption of the STA, number of frames buffered, and average delay per frame are obtained. These results enable an efficient power management algorithm that optimizes the idle timer and doze duration at the STA and the frame buffer at the access point. Moreover, similar statistics for the basic power management method in the IEEE 802.11 standard are derived as a special case of the proposed timer-based power management scheme. Numerical results are presented to demonstrate the effectiveness of the proposed algorithms.

Patent
28 Feb 2010
TL;DR: In this article, a method and apparatus for storing and classifying packets transmitted over a network to a processor in a low power mode is presented, where the processor receives and classifies the packets as interesting or not interesting.
Abstract: A method and apparatus for storing and classifying packets transmitted over a network to a processor in a low power mode. The processor receives and classifies the packets as interesting or not interesting. Uninteresting packets are discarded while interesting packets are stored in memory. For the first interesting packet received, a receive timer is activated and for every interesting packet received a counter is incremented. A transmit timer is activated when the processor enters the low power mode. When either the receive timer expires, the transmit timer expires or the counter reaches a threshold value then a wake-up interrupt is asserted.

Patent
22 Feb 2010
TL;DR: In this article, the APPS-Polling logic is configured to determine a timer value for periodic PS-polling by monitoring a periodicity of arrival packets for at least a threshold amount of time.
Abstract: In accordance with at least some embodiments, a system includes an access point and a station in communication with the access point. The station selectively implements adaptive periodic Power-Save (APPS)-Polling logic for communications between the station and the access point. The APPS-Polling logic is configured to determine a timer value for periodic PS-Polling by monitoring a periodicity of arrival packets for at least a threshold amount of time.

Patent
08 Sep 2010
TL;DR: In this paper, a first awake timer may be started in response to receiving a beacon signal from the wireless access point, which may indicate that data is available or pending for the wireless mobile station.
Abstract: Methods and apparatuses for operating a wireless mobile station configured to communicate with a wireless access point are described. A first awake timer may be started in response to receiving a beacon signal from the wireless access point. The beacon signal may indicate that data is available or pending for the wireless mobile station. A second awake timer may be started in response to data received from the wireless access point. When the second awake timer expires, the wireless mobile station may return to the sleep state. In one embodiment, the first awake timer counts for a first period of time and the second awake timer counts for a second period of time which is shorter than the first period of time. The RF radio may be in a higher power state when the first and/or the second awake timers are counting. In one embodiment, the wireless mobile station and the wireless access points may be synchronized using target beacon transmission times of the beacon signal.

Posted Content
TL;DR: A system, which is able to control eight electric appliances properly in these three modes, is developed, which will play an important role for the elderly and physically disable people to control their home appliances in intuitive and flexible way.
Abstract: The main objective of this work is to design and construct a microcomputer based system: to control electric appliances such as light, fan, heater, washing machine, motor, TV, etc. The paper discusses two major approaches to control home appliances. The first involves controlling home appliances using timer option. The second approach is to control home appliances using voice command. Moreover, it is also possible to control appliances using Graphical User Interface. The parallel port is used to transfer data from computer to the particular device to be controlled. An interface box is designed to connect the high power loads to the parallel port. This system will play an important role for the elderly and physically disable people to control their home appliances in intuitive and flexible way. We have developed a system, which is able to control eight electric appliances properly in these three modes.

Patent
Sunghoon Jung1, Sung Duck Chun1, Seung June Yi1, Youngdae Lee1, Sung Jun Park1 
21 Jul 2010
TL;DR: In this paper, a method and apparatus for handling radio link failure in a wireless communication system is provided, in which a user equipment starts a radio link link failure timer of which timer value is selected among at least one timer value for at least 1 RB.
Abstract: A method and apparatus of handling a radio link failure in a wireless communication system is provided. Upon detecting a radio link failure in a Radio Resource Control (RRC) connected state, a user equipment starts a radio link failure timer of which timer value is selected among at least one timer value for at least one RB. The user equipment attempts a RRC connection re-establishment while the radio link failure timer is running, and transitions to a RRC idle state when the radio link failure timer is expired.

Patent
02 Aug 2010
TL;DR: In this article, an online services system provides monitoring of user interaction with third-party content, which is performed by a script in a web page provided by the online service system, which script provides a timer invoked when the browser leaves the online services page's page for a page comprising third party content.
Abstract: An online services system provides monitoring of user interaction with third-party content. The monitoring is performed by a script in a web page provided by the online services system, which script provides a timer invoked when the browser leaves the online services system's page for a page comprising third party content. When the online services system serves the page, the browser reads the HTML to render the page, including the script with the timer. When the user leaves the online services system page, the timer begins, and when the browser returns to a page provided by the online services system, the timer ends and duration information from the timer is provided to the online services system. Applications include measurement of the quality of interaction between users and a third party advertisers, in which time spent viewing third party content is a proxy for the quality of the interaction.

Patent
Sunghoon Jung1, Sung-Duck Chun2, Seungjune Yi2, Young-Dae Lee2, Sung-Jun Park2 
26 Feb 2010
TL;DR: In this article, a method for operating uplink sync timer among handover in a mobile communication system is provided to use concise handover command which basic MAC setting is included, thereby reducing the amount of wireless resources necessary for handover.
Abstract: PURPOSE: A method for operating uplink sync timer among handover in a mobile communication system is provided to use concise handover command which basic MAC setting is included, thereby reducing the amount of wireless resources necessary for handover CONSTITUTION: A handover command is received from network If a default MAC(Medium Access Control) configuration is included in the handover command, an additional information is received from the network The handover process with the network is performed by using the additional information The default MAC configuration is a setting value which is predetermined between a terminal and the network

Patent
Bruce Kwan1, Puneet Agarwal1
12 Nov 2010
TL;DR: In this article, a data interface is configured to receive data packets from a source endpoint via an intermediate node and the data packets include a field indicating whether data congestion for data being sent to the destination endpoint is occurring.
Abstract: Apparatus and methods for intelligent congestion feedback are disclosed. An example apparatus includes a data interface configured to receive data packets from a source endpoint via an intermediate node. The data packets include a field indicating whether data congestion for data being sent to the destination endpoint is occurring. The example apparatus also includes a timer. The example apparatus further includes a feedback loop interface configured to selectively enable a feedback loop to the source endpoint and to transmit congestion notification (CN) messages to the source endpoint over the feedback loop. Upon receiving a data packet indicating that congestion has occurred due to the data packets from the source endpoint to the destination endpoint, the destination endpoint is configured to set the timer to a preset time value; start the timer reverse counting from the preset time value to zero, enable the feedback loop and transmit the CN messages.

Patent
30 Dec 2010
TL;DR: In this paper, a power conversion system with a feedback control loop is described, and a timer is used to disable the oscillator after a period following the opening of the feedback control loops.
Abstract: A circuit protects a power conversion system with a feedback control loop from a fault condition. The circuit has an oscillator having an input for generating a signal with a frequency and a timer connected to the oscillator input and to the feedback control loop. The timer disables the oscillator after a period following the opening of the feedback control loop to protect the power conversion system.

Patent
16 Nov 2010
TL;DR: In this paper, a system and methodology that performs data bundling and controls fast dormancy based on user interaction with a user equipment (UE) is provided, which provides a balance between saving battery power of the UE and reducing signaling and processing load in a radio resource controller.
Abstract: A system and methodology that performs data bundling and controls fast dormancy based on user interaction with a user equipment (UE) is provided. Moreover, the system provides a balance between saving battery power of the UE and reducing signaling and processing load in a radio resource controller (RRC). Specifically, the system observes user inputs and data flow requests to identify “interactive” and “non-interactive” data flows. On receiving a data flow request, the system determines whether the data flow can be bundled together and transmitted over a single connection with disparate data flows, based on the classification of the data flow. Additionally, on completion of a data flow, the system determines whether a fast dormancy timer can be disabled/delayed to transmit a next data flow over the current connection, based on the classification of the data flow.

Journal ArticleDOI
TL;DR: In this paper, the authors present an algorithm to calibrate manufacturing errors in the cog wheel and interpolate the speed signal to the (usually time) domain of the application, and derive rules of thumb for how sampling and quantization processes influence the bias and variance of the computed speed signal.
Abstract: Rotational speed sensors are critical for all vehicular driver assistance systems and other applications such as engine control and robotics. For many embedded control systems, the accuracy of the computed speed needs to be high, and this puts special demands on the pre-processing of the sensor signal. In a wired centralized solution, the computational unit can get access to the raw square wave signal from the sensor. Without a dedicated wire, the sensor must include a timer, and the cog times tk can be communicated to the processor. These cog times are the input to the algorithms described here, whose purpose is to calibrate manufacturing errors in the cog wheel and to interpolate the speed signal to the (usually time) domain of the application. A further purpose was to derive rules of thumb for how the sampling and quantization processes influence the bias and variance of the computed speed signal. Examples of applications to imbalance monitoring, frequency analysis applications, and fault detection were provided.

Patent
11 Jan 2010
TL;DR: In this article, a data link message from a sender to a receiver, storing the trasmitted message, and starting a message timer when the message is transmitted, is presented.
Abstract: A method for communicating a data link message is provided. The method comprises transmitting a data link message from a sender to a receiver, storing the trasmitted data link message, and starting a message timer when the data link message is transmitted. The method further comprises determining whether a response to the data link message has been received, and determining whether the message timer has expired if the response has not been received. The sender is notified when the message timer has expired and the response has not been received. Input is requested from the sender whether or not to retransmit the data link message. If input is received from the sender to retransmit, the data link message is displayed to the sender for review and edit. The data link message is then retransmitted from the sender to the receiver.

Patent
16 Jul 2010
TL;DR: In this paper, the distributed storage unit can invoke a write lock for all encoded data slices having the same slice name as the slice being currently written, and a rollback timer started.
Abstract: Multiple revisions of an encoded data slice can be stored in a distributed storage unit. Before writing a new revision of an encoded data slice to storage, the distributed storage unit can invoke a write lock for all encoded data slices having the same slice name as the slice being currently written. The slice being currently written can be stored in temporary storage, and a rollback timer started. If a commit command is received before expiration of the rollback timer, the currently written slice can be permanently stored and made accessible for read requests. If the rollback timer expires prior to the storage unit receiving a commit command, however, a previously stored revision will be used.