USB 2.0 vs USB 3.0

USB 3.0, the latest version of USB (Universal Serial Bus), provides better speed and more efficient power management than USB 2.0. USB 3.0 is backward compatible with USB 2.0 devices; however, data transfer speeds are limited to USB 2.0 levels when these devices inter-operate.

Comparison chart

	USB 2.0	USB 3.0
Released:	April 2000	November 2008
Speed:	High Speed or HS, 480 Mbps (Megabits per second)	10 times faster than USB 2.0. Super Speed or SS, 4.8 Gbps (Giga bits per second)
Signaling Method:	Polling mechanism i.e can either send or receive data	Asynchronous mechanism i.e. can send and receive data simultaneously
Price:	For a similar product, the USB 2.0 version is generally less expensive than it's USB 3.0 version.	For a similar product, the USB 3.0 version is generally more expensive than it's USB 2.0 version.
Power Usage:	Up to 500 mA	Up to 900 mA. Allows better power efficiency with less power for idle states. Can power more devices from one hub.
Number of wires within the cable:	4	8
Standard-A Connectors:	Grey in color	Blue in color
Standard-B Connectors:	Smaller in size	Extra space for more wires

What is USB 3.0 and USB 2.0?

Universal Serial Bus (USB) is an industry standard developed in the mid-1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices. Now even devices like smartphones, PDAs and video game consoles are connected to the computers with USB ports allowing recharging and communication thereby replacing the requirement of adapters and power chargers.

USB3.0 was released in November 2008, almost eight years after the release of USB 2.0.

USB 3.0 Highlights and Benefits over USB 2.0                

• Transfer rates - USB 2.0 offers transfer rates of 480 Mbps and USB 3.0 offers transfer rates of 4.8 Gbps - that's 10 times faster.
• Addition of another phsyical bus - The amount of wires has been doubled, from 4 to 8. Additional wires require more space in both the cables and connectors, so there are new types of connectors.
• Power consumption - USB 2.0 provides up to 500 mA whereas USB 3.0 provides up to 900 mA. The USB 3 devices will provide more power when needed and conserve power when the device is connected but idling.
• More bandwidth - instead of one-way communication, USB 3.0 uses two unidirectional data paths, one to receive data and the other to transmit while USB 2.0 can only handle only one direction of data at any time.
• Improved bus utilization - a new feature has been added (using packets NRDY and ERDY) to let a device asynchronously notify the host of its readiness.

When data is being transferred through USB 3.0 Devices, cables and connectors transaction is initiated by the host making a request followed by a response from the device. The device either accepts the request or rejects it. If accepted then device sends data or accepts data from the host. If there is lack of buffer space or data, it responds with a Not Ready (NRDY) signal to tell the host that it is not able to process the request. When the device is ready then, it will send an Endpoint Ready (ERDY) to the host which will then reschedule the transaction.

Physical Differences                                                                    

USB 3.0 Connectors are different from USB 2.0 Connectors and the 3.0 connectors are usually colored blue on the inside in order to distinguish them from the 2.0 connectors.

Various types of USB Connectors (click to enlarge). From Left to Right: Micro USB Type AB, Micro USB Type B, USB 2.0 Type A, USB 2.0 Type B, USB 3.0 Type A, USB 3.0 Type B, USB 3.0 Type Micro B, Min USB Type A connector

Backward Compatible                                                                

USB 3.0 is compatible with USB 2.0. However, the USB 3.0 product will perform at the same level as a USB 2.0 product, so speed and power benefits will not be fully realized.

USB 3.0 receptacles are electrically compatible with USB Standard 2.0 device plugs if they physically match. USB 3.0 type-A plugs and receptacles are completely backward compatible, and USB 3.0 type-B receptacles will accept USB 2.0 and earlier plugs. However, USB 3.0 type-B plugs will not fit into USB 2.0 and earlier receptacles.

This means that USB 3.0 cables cannot be used with USB 2.0 and USB 1.1 peripherals, although USB 2.0 cables can be used with USB 3.0 devices, if at USB 2.0 speeds. 

Price

For a similar product, the USB 3.0 version is generally more expensive than it's USB 2.0 version.

3G Vs. 4G

How much faster is 4G compared to 3G and what applications run better on 4G?

3G and 4G are standards for mobile communication. Standards specify how the airwaves must be used for transmitting information (voice and data). 3G (or 3rd Generation) was launched in Japan in 2001. As recently as mid-2010, the networks for most wireless carriers in the U.S. were 3G. 3G networks were a significant improvement over 2G networks, offering higher speeds for data transfer. The improvement that 4G offers over 3G is often less pronounced. Analysts use the analogy of standard vs Hi-Def TV to describe the difference between 3G and 4G.

Comparison chart:

	3G	4G
Data Throughput:	Up to 3.1mbps	Practically speaking, 3 to 5 mbps but potential estimated at a range of 100 to 300 mbps.
Peak Upload Rate:	50 Mbit/s	500 Mbit/s
Peak Download Rate:	100 Mbit/s	1 Gbit/s
Switching Technique:	packet switching	packet switching, message switching
Network Architecture:	Wide Area Cell Based	Integration of wireless LAN and Wide area.
Services And Applications:	CDMA 2000, UMTS, EDGE etc	Wimax2 and LTE-Advance
Forward error correction (FEC):	3G uses Turbo codes for error correction.	Concatenated codes are used for error corrections in 4G.
Frequency Band:	1.8 – 2.5GHz	2 – 8GHz

Comparison Between A-GPS and GPS

 

A-GPS and GPS are different navigational aids that both use information from satellites to determine their exact location on Earth.

GPS stands for Global Positioning System. A GPS device communicates with 4 or more satellites to determine its exact location coordinates (latitude and longitude) anywhere on Earth. It works in any weather as long as the device has a clear line of sight to the satellites.

A-GPS stands for Assisted Global Positioning System. While it works on the same principles as a GPS (explained below), the difference here is that it gets the information from the satellites by using network resources e.g. mobile network, also called assistant servers.

Comparison chart

	A-GPS	GPS
Stands for:	Assisted Global Positioning System	Global Positioning System
Source of triangulation information:	Radio signals from satellites and assistance servers e.g. mobile network cell sites	Radio signals from GPS satellites
Speed:	A-GPS devices determine location coordinates faster because they have better connectivity with cell sites than directly with satellites.	GPS devices may take several minutes to determine their location because it takes longer to establish connectivity with 4 satellites.
Reliability:	Location determined via A-GPS are slightly less accurate than GPS	GPS devices can determine location coordinates to within 1 meter accuracy
Cost:	It costs money to use A-GPS devices on an ongoing basis because they use mobile network resources.	GPS devices communicate directly with satellites for free. There is no cost of operation once the device is paid for.
Usage:	Mobile phones	Cars, planes, ships/boats