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Wireless Pervasive Computing, 2006 1st International Symposium on

Date 16-18 Jan. 2006

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Displaying Results 1 - 25 of 110
  • Efficient medium access control for wireless sensor networks

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB) |  | HTML iconHTML  

    An efficient medium access control (MAC) protocol is critical for the performance of a wireless sensor network (WSN), especially in terms of energy consumption. In this work we discuss the efficiency of S-MAC, a well-known MAC protocol for WSNs, and propose an improvement on the protocol. Via an extensive simulation study considering the cases of both a simple linear topology and a complicated tree topology used for structural health monitoring, the performance evaluation of the enhanced protocol shows that it outperforms the original version of S-MAC in energy conservation. View full abstract»

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  • Lowest-ID with adaptive ID reassignment: a novel mobile ad-hoc networks clustering algorithm

    Publication Year: 2006
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4920 KB) |  | HTML iconHTML  

    Clustering is a promising approach for building hierarchies and simplifying the routing process in mobile ad-hoc network environments. The main objective of clustering is to identify suitable node representatives, i.e. cluster heads (CHs), to store routing and topology information and maximize clusters stability. Traditional clustering algorithms suggest CH election exclusively based on node IDs or location information and involve frequent broadcasting of control packets, even when network topology remains unchanged. More recent works take into account additional metrics (such as energy and mobility) and optimize initial clustering. However, in many situations (e.g. in relatively static topologies) re-clustering procedure is hardly ever invoked; hence initially elected CHs soon reach battery exhaustion. Herein, we introduce an efficient distributed clustering algorithm that uses both mobility and energy metrics to provide stable cluster formations. CHs are initially elected based on the time and cost-efficient lowest-ID method. During clustering maintenance phase though, node IDs are re-assigned according to nodes mobility and energy status, ensuring that nodes with low-mobility and sufficient energy supply are assigned low IDs and, hence, are elected as CHs. Our algorithm also reduces control traffic volume since broadcast period is adjusted according to the nodes mobility pattern: we employ infrequent broadcasting for relative static network topologies, and increase broadcast frequency for highly mobile network configurations. Simulation results verify that energy consumption is uniformly distributed among network nodes and that signaling overhead is significantly decreased. View full abstract»

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  • A coverage algorithm in 3D wireless sensor networks

    Publication Year: 2006
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3368 KB) |  | HTML iconHTML  

    Wireless sensor networks (WSNs) made up of many small sensing devices equipped with memory, processors, and short-range wireless communication provides an unprecedented amount of detailed measurements over wide geographic areas. Communication between nodes requires the expenditure of energy, a scarce commodity in most WSNs. Thus, making effective use of data require scalable, self organizing, and energy-efficient data dissemination algorithms. In this paper, contrary to existing techniques, the coverage problem in a three dimensional space is analyzed. The "coverage hole" problem is also analyzed and a substitute plan is proposed where sensor nodes that are almost out of energy or already dead, are substituted by nodes that covers their sensing region and have more energy supply. View full abstract»

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  • Asymmetric multihop communication in large sensor networks

    Publication Year: 2006
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB) |  | HTML iconHTML  

    With the growing interest in wireless sensor networks, energy efficient communication infrastructures for such networks are becoming increasingly important. In this paper, we compare and simulate asymmetric and symmetric communication in sensor networks. We do this by extending LEACH, a well-known TDMA cluster-based sensor network architecture, to use asymmetric communication. The extension makes it possible to scale up the network size beyond what is feasible with LEACH and its variants LEACH-C and LEACH-F. View full abstract»

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  • Supporting heterogeneous traffic in wireless sensor networks

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    We consider an energy-aware packet transmission node that supports packets of two types: real-time packets and non real-time packets. Several energy-aware packet scheduling schemes are explored and discussed. Using the average delay of non real-time packets and the rejection rate of real-time packets as performance metrics, a scheduling scheme for this purpose is proposed. It is composed of two scheduling stages. In the early stage, each packet type is scheduled independently on the per type basis. They are then merged using PGPS into the second stage where the transmission speed for each packet is assigned. The packets are then transmitted using dynamic modulation scaling (DMS). The method has been evaluated using simulation and compared against one in which energy savings schemes are not incorporated. The result shows that not only does it provide a fair share of bandwidth (low rejected packets for real-time packets and low delay for non real-time packets) between these streams, but it also saves the overall transmission energy, particularly in the light load case, where as much as 90% savings can be obtained. View full abstract»

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  • An analytical traffic flow model for cluster-based wireless sensor networks

    Publication Year: 2006
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2480 KB) |  | HTML iconHTML  

    An analytical traffic flow model is developed for cluster-based wireless sensor networks. The source-to-sink path is modeled by a number of single-server finite queues linked in tandem. During the process of modeling, both the blocking effect of tandem queuing networks and the impact of connection failure due to limited node power are taken into account. The tandem queuing network is analyzed by decomposing it into individual nodes with modified arrival and service processes and modified queue capacities. The steady-state queue-length distributions of individual nodes are determined iteratively by using the matrix-geometric procedure. A computational algorithm with a global loop from the last node to the first node and local loops in individual nodes is developed to determine the performance metrics, such as source-to-sink throughput (SST) and source-to-sink delay (SSD), of the tandem network. View full abstract»

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  • A service framework for mobile ubiquitous sensor networks and RFID

    Publication Year: 2006 , Page(s): 6 pp. - 6
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1010 KB) |  | HTML iconHTML  

    Recent research in mobile computing envisions a future of "smart environments", where user and computing merge to realize the so called "ubiquitous society". As an exponent of mobile information units, RFID (radio frequency identification) and wireless sensor networks (WSN) play a key roll in this future. In every real-world object, RFID tag information is combined with sensor data to embody "smart" entities. These entities move freely, providing their sensor values and identity and getting in return personalized services anywhere, anytime. Entities interact, creating grouped objects that provide unified and meaningful information, widely extending the available services. But how to control this ubiquitous flow of information? How will users really benefit from it? In this paper we introduced WISSE, a framework that defines the interaction between mobile RFID/WSN entities and the services they receive. View full abstract»

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  • Balancing image quality and energy consumption in visual sensor networks

    Publication Year: 2006
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Applications of wireless sensor networks have attracted a lot of attention recently. Cameras are installed in various locations of a wide area to capture images of targeted objects. Because of constraints in computational capability in these distributed cameras, it may not be feasible to analyze these images in the sensors but they have to be transmitted to a centralized server hop by hop through the sensor network. To reduce the energy used in transmission, the size of the images should be kept small by applying a large compression ratio, which may degrade image quality. This paper studies the tradeoff between image quality and energy consumption. We study the scenario that a number of camera-equipped sensors are taking pictures of the same object, and the pictures of adjacent cameras may overlap. We demonstrate that by allowing intermediate sensors to process the images and combine the overlapping portions, the total energy spent on transmission is reduced subject to a certain degradation in image quality. The tradeoff between image quality and energy consumption of different routing presents an important study on the practicability of visual sensor networks. View full abstract»

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  • New Orthogonal Code with MPSK for Next-Generation CDMA Systems

    Publication Year: 2006 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2816 KB) |  | HTML iconHTML  

    A novel Orthogonal Expanded Walsh Code (OEWC) suited in DS-CDMA spreading is presented in this paper. Although some processing gain increased, the OEWC can increase channel anti-interference and transmission security since of its elongated horizontal length. Moreover, it can be applied with MPSK to modulate one of M signal units expressed with a chip of OEWC. This plus the higher security and anti-interference abilities make OEWC of interest to designers of next-generation CDMA systems. View full abstract»

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  • Effects of digital filtering technique in reducing the effects of clipping of an enhanced orthogonal frequency division multiplexing system

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6104 KB) |  | HTML iconHTML  

    Despite of the many advantages of OFDM, it has two main drawbacks which are high peak to average power ratio (PAPR) and synchronization problem. High PAPR causes saturation in power amplifiers, leading to intermodulation products among the sub carriers and disturbing out of band energy. Therefore, it is desirable to reduce the PAPR by means of PAPR reduction schemes. However, it caused the degradation of BER and enhanced the growth of out of band radiation which has led to the degradation of OFDM overall performance. In this paper, OFDM system with an enhanced clipping technique has been proposed, the effects of clipping have been analyzed and the system is evaluated by integrating with its significant features including convolutional forward error control coding, oversampled inverse fast Fourier transform (IFFT) and digital filtering technique in order to minimize the effects of clipping. It is shown that the bit error rate (BER) of the clipped OFDM signal is improved, the PAPR is further reduced and the effect of out of band radiation is minimized. Besides, other effects of the filtering technique are also analyzed in order to optimize the overall performance of our proposed system. View full abstract»

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  • A Novel Adaptive Reception Technique for Satellite-DMB systems in a Rician Channel

    Publication Year: 2006 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2240 KB) |  | HTML iconHTML  

    Satellite-Digital Multimedia Broadcasting (S-DMB) systems make it possible to watch the televisions on the hands as well as in the vehicular outside. But in case of handheld version of terminal, especially S-DMB phone, there are several challenging issues, which have not been seen in the other terminals. One of these issues is short viewing time, which is caused by limited battery. In this paper, we propose an Adaptive Reception Technique (ART) which provides power saving when the line-of-sight path exists from the satellite. By launching the Frame Selection Control (FSC) at the receiver and modifying the puncturing algorithm, we can simply employ ART and reduce power consumption by about 17.5∼25.5%/. View full abstract»

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  • Performance enhancement of an MB_OFDM based UWB system in multiple SOPs environments

    Publication Year: 2006
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3512 KB) |  | HTML iconHTML  

    In this paper, we propose a new transmission scheme to support multiple simultaneously operating piconets (SOPs) in an ultra wideband (UWB) system based on multi-band orthogonal frequency division multiplexing (MB_OFDM), where the code division technique is combined with the MB_OFDM. When there are 2 or 3 SOPs, the collision between different piconets is increased and the average probabilities of symbol collision increase up to nearly 55.7% and 70.7%, respectively. Hence, the previous scheme using symbol repeater and erasure can't effectively reduce the co-channel interference (CCI). We propose to use the MC_CDMA to mitigate the CCI from 2 and 3 SOPs. Our simulation results demonstrate that the proposed scheme is effective in multiple SOPs. View full abstract»

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  • Joint Multipath Delay Tracking and Interference Cancellation in DS-CDMA Systems Using Successive ICA for Oversaturated Data

    Publication Year: 2006 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    A recent idea is to use blind source separation (BSS) methods within successive interference cancellation (SIC) in DS-CDMA reception. This has been found to results in an interference cancellation solution, that is able to i) mitigate different kinds of interference sources (e.g. multi-access, multi-path and out-of-cell interferences) simultaneously, ii) tackle "more sources than observations"-problem and, consequently, operate in highly loaded systems and iii) deal with imperfect channel estimation better than conventional BSS receiver and conventional interference cancellation. Thus far however, a single path channel has been assumed in studies behind these findings. In this paper we extend our previous studies to multipath channels where inter-path interference hardens the joint delay tracking and interference cancellation problem even more. View full abstract»

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  • PAPR Reduction Method for OFDM Signal by Using Dummy Sub-carriers

    Publication Year: 2006 , Page(s): 1 - 5
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB) |  | HTML iconHTML  

    One of the disadvantages of using OFDM is the larger peak to averaged power ratio (PAPR) in its time domain signal. The larger PAPR signal would course the fatal degradation of bit error rate performance (BER) due to the inter-modulation noise in the non-linear channel. This paper proposes an improved DSI (Dummy Sequence Insertion) method, which can achieve the better PAPR and BER performances. The feature of proposed method is to optimize the phase of each dummy sub-carrier so as to reduce the PAPR performance by changing all predetermined phase coefficients in the time domain signal, which is calculated for data sub-carriers and dummy sub-carriers separately. To achieve the better PAPR performance, this paper also proposes to employ the time-frequency domain swapping algorithm for fine adjustment of phase coefficient of the dummy subcarriers, which can achieve the less complexity of processing and achieves the better PAPR and BER performances than those for the conventional DSI method. This paper presents various computer simulation results to verify the effectiveness of proposed method as comparing with the conventional methods in the non-linear channel. View full abstract»

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  • A Viterbi decoder with low-power trace-back memory structure for wireless pervasive communications

    Publication Year: 2006
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    This paper presents a new trace-back memory structure for Viterbi decoders that reduces power consumption by 63% compared to the conventional RAM based design. Instead of the intensive read and write operations as required in RAM based designs, the new memory is based on an array of registers connected with trace-back signals that decode the output bits on the fly. The structure is used together with appropriate clock and power-aware control signals. Based on a 0.35 μm CMOS implementation the trace-back back memory consumes energy of 182 pJ. View full abstract»

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  • Performance comparison of EV-t and MUSIC for two-dimensional code acquisition

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    In this paper, an efficient method is proposed for joint time delay and direction-of-arrival (DOA) estimation, called two-dimensional code acquisition here, in direct-sequence code division multiple access (DS-CDMA) systems. Meanwhile, we present a rigorous statistical analysis for this method. Through performance comparison with traditional MUSIC, we see the proposed method is robust in highly correlated and coherent multi-path propagation environment. It is effective against channel interferences, and its performance increases with the length of the space-time response vector. View full abstract»

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  • Impact of double-Rayleigh fading on system performance

    Publication Year: 2006
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    Double-Rayleigh amplitude distribution, induced by double scattering in the radio channel, occurs in a variety of propagation scenarios, including propagation via diffracting wedges. It is unknown, however, how double scattering affects communication link performance. In this paper, an expression for symbol error probability for some common communication schemes over double-Rayleigh fading wireless channels is derived. It is shown that double scattering results in severe degradation in symbol error probability. Interestingly, our analysis suggests that for the double-Rayleigh channel there exists no meaningful diversity order for the SNR values of practical interest. View full abstract»

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  • Analysis of energy consumption of IEEE 802.11 DCF under non-saturation conditions

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    We develop an analytic model to evaluate non-saturation energy consumption of IEEE 802.11 DCF, based on the model in G.R. Cantieni et al., (2005). The model explicitly takes into account both the carrier sensing mechanism and an additional backoff interval after successful frame transmission, which can be ignored under saturation conditions. The probability generating function with respect to energy consumed between consecutive frame generations is derived. Numerical example shows that most of the energy is wasted in carrier sensing when the frame generation probability is smaller than some critical value and that the energy consumed in overhearing a frame destined to another user occupies the major part otherwise. View full abstract»

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  • Design of a downlink power control scheme in multi-code CDMA mobile medicine system

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3152 KB) |  | HTML iconHTML  

    In this paper, we proposed a downlink power control scheme to apply in the multi-code CDMA mobile medicine system. The mobile medicine system contains: (i) blood pressure and body temperature measurement value, (ii) medical signals measured by the electrocardiogram device, (iii) mobile patient's history, (iv) G.729 audio signal and MPEG-4 CCD sensor video signal. By the help of the multi-code CDMA spread spectrum communication system with downlink power control strategy to make it possible for transmission media in this system to meet the quality of service of mobile medicine system, and achieve the purpose of the maximum resource utilization. In different media, the power is controlled according to the demand for bit error rate. Higher transmission power is given to the media requesting lower bit error rate. Numerical analysis shows that the ratio of transmission power of voice, video and data virtual channels are approximately 1:2:13 when the bit error rates for the voice, video and data are set at 10-3, 10-4 and 10-7. It is similar to the ratio of SNIR of voice, video and data transmission requirement. Meanwhile, we also test related mobile medical signal transmission and simulation. View full abstract»

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  • A measurement based model for UMTS DL DCH dynamic bearer type switching

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    3GPP specifications allow to change the physical resources allocated to the users dynamically to optimize the radio resource utilization in UMTS. Network operators can make use of this optimization feature by properly adjusting dynamic bearer type switching in their networks. In this paper we show an analysis of the dynamic bearer type switching based on measurements in a live UMTS network in the city center of Vienna, Austria. Particularly, we present the usage probability and the runlength distribution of the three different radio access bearers which are used for transmission over the UMTS DCH (dedicated channel) packet switched (PS) domain in DL (down link), namely 384 kbit/s, 128 kbit/s and 64 kbit/s bearer. For the performance evaluation of applications, system level simulators are used, where the lower layers are usually represented via stochastic models. Following the measured statistics we develop a model capable of properly describing the dynamic switching between the mentioned bearers. Furthermore, we show that a four-state Markov model with its geometrically distributed runlengths does not provide sufficient accuracy. We achieve an enhancement by using a four-state renewal process with Weibull distributed runlengths as presented in this document. View full abstract»

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  • A framework for personal mobile agents in wireless pervasive computing environment

    Publication Year: 2006
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3992 KB) |  | HTML iconHTML  

    We propose a framework architecture for a personal mobile agent that can be used in a wireless pervasive computing environment to help the user to access the relevant information/services. Challenges and approaches for making mobile agents functional in this type of environment are discussed. Primary focus of the paper is in maintaining and using models of the user, environment, and other agents. Also covered are the performance and security related areas. View full abstract»

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  • Minimizing unnecessary notification traffic in the IMS presence system

    Publication Year: 2006
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6712 KB) |  | HTML iconHTML  

    Presence is an always-on service. This means that even when the user does not need presence information about his buddies, his mobile phone gets updates about their state. These updates use bandwidth on the radio network and - even more important - drain the mobile terminal's battery. This paper suggests ways to reduce these updates within the presence part of the 3G IP multimedia subsystem (IMS) while maintaining full responsiveness of the presence service for the end user. We propose and compare three solutions to the problem. They extend the interface between the resource list server and the mobile terminal. Our methods minimize traffic on the air interface while maintaining full responsiveness for the end user. They are transparent to the presence server and the presentities, the only entities needing adaptations are the client on the user terminal and the resource list server. View full abstract»

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  • Mobile path loss characteristics for low base station antenna height in different forest densities

    Publication Year: 2006
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4168 KB) |  | HTML iconHTML  

    This paper presents studies of propagation in a suburban forest based on a measurement campaign at a frequency of 1.8 GHz. We investigated how tree density affected path loss-distance and the fast fading characteristic depending on the base tree size and base station antenna height in a range of 3, 4, and 5 m above ground while the receiving antenna height was fixed at 1.8 m above ground. The path loss exponent is found that to average 3.8, 3.7 and 2.2 for the measurement areas of high, medium, and low densities respectively. The high density area with low tree heights provides maximum path loss exponents. Path loss in the same density area depends on the number of trees in the direct path between the transmitter and the receiver. The measurement of signal variation shows that a multi-path contribution becomes more significant as the base station antenna is raised. View full abstract»

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  • Angle-of-Arrival Estimation for UWB Signals Clustered in Angle

    Publication Year: 2006 , Page(s): 1 - 4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    In this study, the new signal model suitable for ultrawide band (UWB) environments with random angle spread is proposed to estimate the angle-of-arrivals (AOAs) of clusters in a UWB indoor or indoor-to-outdoor wireless communication. The estimation technique based MUSIC algorithm is investigated and the estimates of the AOA and distribution parameter on the received clusters are obtained. The proposed model and estimation technique are verified using computer simulations, and the performance of the estimation error is analyzed. View full abstract»

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  • A new routing algorithm for micro-mobility by using core node

    Publication Year: 2006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3656 KB) |  | HTML iconHTML  

    In order to provide fast handover, lots of micro-mobility protocols have been designed and proposed. However, they may cause excessive signal traffic and long latency for handover management. This paper proposes a new routing algorithm for micro-mobility scheme using core node. Core node handles routing information for a mobile host. It does not need to generate unnecessary control messages at each base station and wired node. We have conducted distribution of traffic as messages which create at the old BS and then disappears at the core node for maintenance of the routing table. We have evaluated the performance of our micro-mobility scheme through a series of simulations using the network simulator 2 (ns-2). View full abstract»

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