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WLAN
Why use WLAN
For one of the main local area network management, for the laying of cables, or check the cable is disconnected this time-consuming work, it is easy to upset, not easy to break in a short time to find out where. Furthermore, for the business and application environment constantly updating and development of enterprise network must be matched with the original re-layout, need to re-install the network lines, although the cable itself is not expensive, but requested the technical staff to the high cost of wiring, especially the old building, wiring project costs even higher. Therefore, the construction of wireless local area network has become the best solution.
What conditions need to use WLAN
WLAN is not limited to alternative local area network, but to make up for lack of wired local area networks, in order to achieve the purpose of extending the network, the following circumstances may have wireless local area network.
l no fixed workplace users
l wired local area network set up by the environmental constraints
l As a wired local area network backup system
WLAN access technology
Currently manufacturers in the design of wireless local area network products, there are quite a variety of access design methods can be divided into three categories: narrowband microwave, spread spectrum (Spread Spectrum) technology, and infrared have their advantages and disadvantages, limitations, and more, followed by detailed discussion of these techniques. (Infrared) technology, each technique has their advantages and disadvantages, limitations, and more, followed by detailed discussion of these techniques.
Technical requirements
As wireless local area network needs to support high-speed, burst data services, need to be addressed in the indoor use of multipath fading, as well as issues such as crosstalk subnets. Specifically, wireless local area network must achieve the following technical requirements:
1) Reliability: Wireless LAN system packet loss rate should be lower than 10-5, the error rate should be lower than 10-8.
2) Compatibility: For indoor use of wireless local area network, so as far as possible with the existing wired LAN network operating system and network software compatible.
3) Data rate: In order to meet the needs of local area network traffic, wireless LAN data transfer rate should be more than 1Mbps.
4) The confidentiality of communications: As the data transmitted in the air via wireless media, wireless local area networks at different levels must take effective measures to improve communication security and data security.
5) Mobility: support for all mobile networks or semi-mobile network.
6) Energy Management: When receiving or sending data to the site when the machine is in sleep mode, when activated again when the data transceiver to achieve the savings in power consumption.
7) small size and low price: This is the key to the popularity of wireless local area network can be.
8) Electromagnetic environment: wireless LAN should consider the humanbodyand the surrounding electromagnetic environment effects.
Android
Google Android is a Linux-based platform for developing open-source phone operating system (registered trademark in China called "Achi;). It includes operating systems, user interface and applications - mobile phone work required by the software, but there is no past, the exclusive right to impede innovation and barriers to mobile industry, called mobile terminal is the first to create a truly open and complete mobile software. Google and Open Handset Alliance to develop the Android, the alliance by including China Mobile, Motorola, Qualcomm and T-Mobile, including more than 30 technology and the composition of a leader in wireless applications. Google with operators, equipment manufacturers, developers and other interested parties to form deep-level partnerships, hoping to establish a standardized, open software platform for mobile phones in the mobile industry to form an open ecosystem .
It uses software stack layers (software stack, also known as the software stack) architecture, is divided into three parts: the core of the underlying Linux-based language developed by the c, only basic functions. Middle layer consists of library. Library and Virtual Machine Virtual Machine, developed by the C +. At the top are a variety of applications, including the call procedures, SMS procedures, application software is developed by the companies themselves to write java.
To promote this technology, Google, and dozens of other phone company has established the Open Handset Alliance (Open Handset Alliance).
Characteristic
l application framework to support component reuse and replacement
l Dalvik virtual machine specifically for mobile devices is optimized
l Internal integrated browser, the browser-based open-source WebKit engine
l optimization of 2D and 3D graphics library includes graphics library, 3D graphics library based on OpenGL ES 1.0 (hardware-accelerated optional)
l # SQLite for structured data storage
l Multimedia support includes the common audio, video and static image file formats (such as MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
l GSM phone (depending on hardware)
l Bluetooth Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
l Camera, GPS, compass, and accelerometer (hardware dependent)
l Rich development environment including a device emulator, debugger, memory and performance analysis charts, and the Eclipse integrated development environment plug-ins
Applications
A core Android application package together with the release of the application package, including email client, SMS short messaging program, calendar, maps, browser, contact management procedures. A ll applications are written using JAVA.
Android Application Framework Developers have full access to core applications used by the API framework. The application framework designed to simplify the reuse of software components; any application can publish its functional blocks and any other applications can use the function block its release (but must follow the framework of security restrictions). Reuse mechanism allows the application form can be user replaced.
All of the following applications by the composition of a range of services and systems, including:
l an expanded view (Views) can be used to build applications, including a list of (lists), grid (grids), text boxes (text boxes), buttons (buttons), and even an embeddable web browser.
l Content Manager (Content Providers) allows applications to access data from another application program (such as the contact database), or to share their own data.
l A resource manager (Resource Manager) to provide access to non-code resources, such as local strings, graphics, and hierarchical file (layout files).
l A notification manager (Notification Manager) allows applications to customers in the status bar display notification information.
l An activity class Manager (Activity Manager) to manage the application life cycle and provides common navigation rollback feature.
Ordering the system
Ordering the system information using automated software tools to achieve la carte, side dishes, stir fry vegetables to the transfer of all management processes; completion point, the computer management menu, point the menu and the kitchen, front-end checkout synchronization print; achieved without the menu paper-based operation; backstage manager of inquiry; warehouse inventory management and so on.
In addition, ordering the system can also effectively manage customer data, archiving and future reference, put an end to the restaurant "leakage List", "run list" phenomenon; help restaurants using computer data processing capability and powerful ability to process optimization to achieve automated management, streamline workflow restaurant, reduce waste and man-made phenomenon of management oversight, re-optimal allocation of corporate resources, the operating costs to a minimum.
Powerful addition to ordering the system to support the general application of stand-alone and LAN in addition to support head office / branch of multi-level framework used for remote network using the POS system to achieve front store sales cashier, sales of small-ticket instantly print sales day-end, reporting sales data and receive information of new features dishes.
There are three currently ordering the system to achieve mode:
First, the touch screen a la carte model: It uses the currently most popular touch-computer ordering process to achieve that members can to order the software screen prompts, simply click on the screen with your fingers can complete the entire ordering process and convenient This model applies to the practice of rich dishes and large restaurants, restaurants, and restaurant, etc..
Second,the wireless PDA ordering mode: it uses a wireless WiFi technology, a la carte interface by PDA display, use touch pen to complete the ordering process, virtually anywhere, anytime to order real-time response, this model is more suitable for dishes and practices simple restaurant, features a restaurant and special mood of senior restaurants.
Third, the wireless ordering Po mode: it uses the ISM band, can be a floor or other obstruction in the case of seamless coverage up to 10 meters away, while the signal remained stable, which is the ratio of the wireless PDA ordering model's greatest strength, this model applies to simple dishes and practices and other requirements with fewer fast food restaurants, pot shops.
