General Packet Radio Service (GPRS)

GPRS protocol is a packet-switch protocol; define for web applications in GSM network. In other words Internet on GSM network is standardized as GPRS network. GPRS has digital structure and this structure based on Time Division Multiple Access (TDMA) technique. One TDMA frame has 8 time slots (TSs). These TSs can be allocated to users, and single TS can be shared by several active users for uplink and downlink purposes. Different coding schemes are used to enhance data rate from 9Kbps to 150 Kbps per user, and it takes 0.5 to 1 second. Security features in GPRS is provided by GSM network.

GPRS Architecture

Global System for Mobile Communication (GSM) circuit-switch architecture does not support the GPRS packet-switch architecture. Thus, GPRS requires its own network architecture. Several networks and databases e.g. Mobile Station (MS), Base Station Subsystem (BSS), Home Location Register (HLR), Visitor Location Register (VLR) in existing GSM network are modified in GPRS network.

GPRS architecture introduces the following network nodes to GSM architecture.

• Serving GPRS Support Node (SGSN)

• Gateway GPRS Support Node (GGSN)

• Mobile Station (MS)

• Base Station System (BSS)

• Home Location Register (HLR)

• Visitor Location Register (VLR)

1.Serving GPRS Support Node (SGSN): In GPRS network SGSN is equivalent to MSC. Packets of data between MSC and Public Switch Data Network (PSDN) are transferred and received by SGSN.

2.Gateway GPRS Support Node (GGSN): GSM databases e.g. HLR and VLR are supported by GGSN. It also interacts with external packet-switch networks.

3.Mobile Station (MS): In GPRS network MS consists of Mobile Terminal (MT) and Terminal Equipment (TE). A computer attached to MT is called a ME. Through air, MT communicates with the BSS.

4.Base Station System (BSS): In BSS, Base Transceiver Station (BTS) and Base Station Controller (BSC) are modified to support GPRS channel coding schemes BTS is modified while to forward calls to Mobile Switching Centre (MSC) and data to SGSN through Packet Control Unit (PCU), is supported by BSC. One SGSN is served by one BSC.

5.Home Location Register (HLR): In GPRS, HLR contains information about routing. To map an MS to one or more GGSNs, update the SGSN and to store the Internet Protocol (IP) address, this information is accessed by both SGSN and GGSN.

6.Visitor Location Register (VLR): In GPRS. VLR contains the SGSN number and this number indicates the MS currently served by the SGSN.

GPRS functional Groups

The functions which are defined in GPRS are following.

• Network access function: Point to point data transfer, registration of MS with packet data protocols, radio resources for MS communication and charging information about packet transmission, is provided by this function.

• Packet routing and transfer function: Routing of data between an MS and destination, conversion of GPRS address to external address and forwarding of packets between an MS and GGSN, is provided by this function.

• Logical link management function: The communication between an MS and the GSM network is maintained by it.

• Radio resources management function: Radio communication paths are allocated by it.

• Mobility management function: Current location of an MS is kept by it. When an MS is entered to a new area, all routing and location in formations are also updated by it.

• Network management function: If provides mechanisms to support network functions related to GPRS.

Advantages

The major advantage of GPRS is that, to access data no dial-up connection is required. It is an inexpensive mobile data service as compared to Short Message Service (SMS) in GSM.

USB 2.0 - Hi-Speed USB - FAQ

What is USB 2.0?
USB 2.0 is a complete overhaul to the Universal Serial Bus input/output bus protocol which allows much higher speeds than the older USB 1.1 standard did.

USB 1.1 allowed a maximum transfer rate of 12Mbits/second. That rate is now called 'USB.' Though some manufacturers label their products Full-Speed USB. Note that this seems a bit deceptive. Its easy to mistake Full-Speed for Hi-Speed.

As an aside, USB mice and keyboards need only 1.5Mbits/s to function. That performance level is also named 'USB' by the USB Promoter Group.

To sum it up, USB 2.0 specification incorporates three speeds: Hi-Speed, Full-Speed and Low-Speed. You as a consumer don't need to figure out all the jargons. Just keep in mind that only 'Hi-Speed USB' and 'USB' host and devices exist.

How do I know if my PC has USB 2.0?
You can identify whether your PC has Hi-Speed or not relatively easy. Open Device Manager and expand the Universal Serial Bus section. There should be an "Enhanced" USB host controller present.

Windows 98 systems may use a different name, because Hi-Speed USB drivers in these operating systems are not provided directly from Microsoft (Windows ME, 2000 and XP get their drivers through Windows Update).

These drivers are provided by the manufacturer, and may carry the maker's name (i.e. ADS, Belkin, IOGear, Siig, etc.). There should also be two standard version USB host controllers present as well. They are embedded in the USB chip which routes the differing USB speeds accordingly without user intervention.

There are currently 6 manufacturers of the Hi-Speed USB host silicon themselves:

• ALi (Acer Labs)

• Intel

• NEC

• SiS

• VIA

• nVidia (shows as "Standard" controller

Any other brand name that appears in Device Manager would likely be an add-in Hi-Speed USB PCI card. The makers above do not make add-in cards, but they do make the chips that are used in them.

How do troubleshoot "unknown device" error listed in Device Manager?

• The USB device or the USB adapter requires its own power source. If your USB device or adapter came with an AC power "brick", try connecting it.

• Here's a likely one - the front USB ports on your PC case may be misconnected. I've seen them that way from the factory. It's a good idea to check the connections against specifications. The standard order of connection is Red, White, Green, and Black. No more than 4 wires per USB bank are needed.

• Defective device. Do not assume that all PC components work correctly out of the box. I've seen many new USB devices that do not work. If you can, try the device on another PC.

• All drivers are not installed. Some devices will require installing the driver package before plugging in the device. Some devices will also require basic USB files from the Windows CD before the unit will function. The general rule is to always follow installation directions precisely and to have the Windows CD ready.

How fast is USB 2.0?
USB 2.0 has a raw data rate at 480Mbps, and it is rated 40 times faster than its predecessor interface, USB 1.1, which tops at 12Mbps. Originally, USB 2.0 was intended to go only as fast as 240Mbps.

How will consumers benefit from USB 2.0?
With speed 40 times more than that of USB 1.1, USB 2.0 broaden the range of external peripherals that can be used on a computer. Even with multiple high-speed peripherals connected to a USB 2.0 bus, the system will less likely to hit the bandwidth bottleneck. The new specification also inherits the current USB's Plug and Play and hot-swapping capability as well as providing backward compatibility for USB 1.1 hardware, allowing existing user base to upgrade seamlessly.

Do USB 2.0 & USB 1.1 hardware work interchangeably?
You may have heard that USB 2.0 is "backward-compatible" with USB 1.0/1.1 (Full-Speed USB). While that's true, USB 1.1 is also forward-compatible with USB 2.0. Whenever a system has USB 2.0 ports, you'll find the "Enhanced" USB controller in Device Manager, but you will also find two other USB controllers. These two to maintain backward compatibility to USB 1.1 devices. Each USB 2.0 host actually has 3 chips onboard. The USB controller routes signals to the correct controller chip depending on how a device is recognized. Where a device is physically plugged in has no bearing on how it is routed. All ports on a USB 2.0 motherboard can host any USB devices at all as long as the system and devices are healthy.

The vast majority of USB 2.0 devices will work on older PCs and Macs. None should flat-out fail unless there are other issues with the system. Hi-Speed USB devices will revert to Full-Speed operation when connected this way. Understand that Hi-Speed is at least ten times faster than Full-Speed in actual operation, so the speed difference is quite noticeable - unless you have never experienced Hi-Speed, of course.

When it comes to USB hub compatibility between USB 2.0 and USB 1.1, here some facts:

• A powered hub is always preferable to unpowered.

• USB hub ports are not as capable or flexible as real PC ports so it's best not to expect the world of them.

• USB 1.1 (obsolete) hubs will work fine on USB 2.0 ports, but they cannot utilize USB 2.0 capabilities. They will default to slower speeds.

• Hi-Speed and Full/Low-Speed USB devices can coexist nicely on USB 2.0 hubs. Connecting such a hub to a USB 2.0 port is recommended.

• USB 2.0 hubs can be used on older USB 1.1 computers.

• Although it is said that you can "cascade" up to 4 hubs, problems may start to arise after two hubs, it's best to minimize hub usage if possible.

• Many USB devices don't work well on hubs. Cameras, scanners and especially USB drives are known to have problems with hub connectivity.

• Remember that "active USB extensions" are really just one-port hubs.

Will USB 2.0 replace USB 1.1?
Not entirely, because many products such as generic keyboards, mice, joysticks and audio speakers do not require the faster speed of the new USB 2.0 technologies. Only bandwidth-hungry devices, such as web cams and high-capacity storage systems, will need all the speed. However, next-generation systems will come with USB 2 ports rather than USB 1.1.

How do I distinguish between a USB 2.0 and a USB 1.1 devices? New logos designed by the USB Promoter Group allow consumers to easily identify the new USB 2.0 products. The new colorful logo for USB 2.0 is labeled USB Hi-Speed, and the new logo for USB 1.1 is labeled with USB Basic Speed. However, most people won't miss it as manufacturers often label USB 2.0 READY Or 40 times faster than USB 1.1, on the boxes.

Will USB 1.1 devices run any faster on a USB 2.0 bus?
No. However, the new USB 2.0 archiclecture allows more high-speed USB 1.1 devices, such as web cams, audio devices, to share the bandwidth. Developers need to follow USB 2.0 spec in order to design higher speed peripherals that can take advantage of the extra bandwidth. USB 1.1 devices still operate at 12Mbps at full-speed and 1.5Mbps at low-speed on a USB 2.0 bus. Even though USB 1.1 devices won't run any faster, they can work alongside of USB 2.0 devices on the same bus.

What are USB Hi-Speed and USB Basic Speed logos?
These logos are part of USB Promoter Group's branding program that ensures the quality of USB products. The USB 2.0 certified products would display a blue, white and red logo, bearing the words Certified and Hi-Speed. The classic USB 1.1 certified products would display a black and white logo with the words USB and Certified.

Under a license from USB-IF, products must pass the compliance tests before manufacturers can use one of the two trademarked logos. The Promoter Group will take legal actions on manufacturers that label either logo on their products, which have not passed the tests.

What happen if a USB 2.0 devices are plugged into a USB 1.1 systems?
The entire bus under the USB 1.1 root hub will slow to 12Mbps. The operating system will probably notify the user about the sub-optimal configuration and recommend for a better course of action.

If several USB 1.1 hubs are connected to a USB 2.0 bus, then each of the USB 1.1 hubs will get a full 12Mbps bandwidth.

What is the max? Length of a USB 2.0 cable?
5m. however, if you cascade 5 hubs with 5m USB cables, this will allow you to connect a device 30m away.

What do I need to use a USB 2.0 device?
The requirement is similar to that of USB 1.1, but all components will have to be USB 2.0 compliant. A successful USB 2.0 connection requires a USB 2.0 host controller card, a USB 2.0 driver and a USB 2.0 peripheral.

How much will it cost to upgrade to USB 2.0?
Around $80 to $150. Currently, Orange Micro., Adaptec and IO Gear are shipping USB 2.0 PCI cards, some of which even have FireWire ports. Interestingly, almost all USB 2.0 PCI cards include an internal port, which is probably for connecting internal USB 2.0 IDE enclosure or USB 2.0 front panel.

Will USB 2.0 arrive on mobile computers?
Yes, but not in integrated solution on laptops. You will need a USB 2.0 Card Bus card. Orange Micro. is shipping USB 2.0 compliant 4-port Card Bus card. Eventually, notebook vendors will adapt to USB 2.0 technology, and we will see USB 2.0 ports on laptops. This transition won't happen until 2002 at the earliest.

Which operating systems support USB 2.0?
Microsoft has released the official USB 2.0 driver for Windows XP and Windows 2000. The version is 5.1.2600. The software is available on-line at Windows Update website. (If you don't have a USB 2.0 card installed in your system, Windows Update won't list the USB 2.0 driver as an update.)

The software company is still considering USB 2.0 support for Windows ME, but it already has decided not to bring USB 2.0 to Windows 98 and Windows 98 SE. If you have Windows 98, you will have to rely on 3rd party USB 2.0 support from USB card manufacturer.

Do USB 1.1 cables work with USB 2.0 devices?
Ideally, yes. USB 2.0 architecture uses the same cables and connectors as USB 1.1 compliant products. Unfortunately, only 3 out of 11 cables on the market are certified as USB 1.1 compliant. You may run into the cables that cause problems connecting high-speed peripherals. To avoid negative user experience, most vendors include USB 2.0 compliant cables with their USB 2 PCI cards and peripherals.