4G: Wireless Broadband

G Wireless Broadband

Despite the fact that we have not yet fully implemented 3G and 3.5G technologies, 4G (which the IEEE officially calls "3G and Beyond") is already on its way, posing a major detriment for the future of 3G. In general, a generation is defined by the technology changes over a 10- to 15-year period, so 4G refers to whatever will be deployed in the 20102015 time frame.

The introduction of 3G technology provides a huge expansion in mobile capacity and bandwidth. 4G will do the same for the spectrum of broadband communications. By supporting mobility, and by being faster and cheaper to deploy, it is expected that 4G will disrupt today's wired broadband access alternatives, including DSL and cable modems. 4G is also expected to serve the next billion Web users in developing countries. Generally speaking, 4G is an evolution not only to move beyond the limitations and problems associated with 3G but also to increase the bandwidth, enhance the quality of services, and reduce the cost of the resource. The main distinguishing characteristics between 3G and 4G will be increased data rates, enhanced multimedia services, new transmission techniques, new Internet access technology, greater compatibility in interfacing with wired backbone networks, and the addition of QoS and security mechanisms. 4G should also be able to provide smooth global roaming ubiquitously, at lower cost. At the very least, this means a new air interface supporting higher data rates and also a change in the way data transport is handled end to end. Unlike 3G networks, which are a mix of circuit-switched and packet-switched networks, 4G will be based solely on packet switching.

The major telecommunications players are already lining up behind their picks for success in the next generation. Intel (www.intel.com), working with startup Beceem Communications, Inc. (www.beceem.com), will begin putting WiMax silicon in notebooks starting in 2007, while Qualcomm (www.qualcomm.com) is expected to put the Flash-OFDM technology in handset chips. Sprint Nextel (www.sprint.com) is studying both technologies, as well as options on the CDMA and GSM roadmaps, as it plans to upgrade its CDMA cellular network in 2008 to 3Mbps in an attempt to compete with DSL and cable. Sprint Nextel conducted one successful trial of the Flash-OFDM technology in 2005 and plans additional trials of Flash-OFDM and WiMax in 2006. Sprint Nextel expects to offer 4G services to the top 100 U.S. markets by 2008.

Some countries have already begun cooperating on 4G standards. In late 2005, Japan and China signed a memorandum to work together on 4G. Japanese carrier NTT DoCoMo claims its 4G prototype phones can receive data at 100Mbps while moving and at 1Gbps while standing still; at these rates, an entire DVD could be downloaded within a minute. DoCoMo's current 3G phone network offers download speeds of 384Kbps and upload speeds of 129Kbps, and the company plans to have a 4G network in place by 2010. The technology behind NTT DoCoMo's high-speed phone network remains experimental, but the 4G tests used a method called Variable-Spreading-Factor Orthogonal Frequency Code Division Multiplexing (VSF-OFCDM), which increases downlink speeds by using multiple radio frequencies to send the same data stream. MIMO was also used to further increase data capacity (e.g., by sending data via various routes across a network); it can enable a mobile phone to receive data from more than one base station in range.

4G should support a wide range of data rates, including at least 100Mbps peak rates in full-mobility wide area coverage and 1Gbps in low-mobility local area coverage. The 4G vision includes asymmetrical and symmetrical services. It provides for QoS for real-time services, supports streaming audio and video, and provides an efficient transport of packet-oriented services, as well as a vision that supports broadcast and distribution services. It supports smart, adaptive antennas and uses an adaptive modulation or coding scheme. One of the main concerns about 4G is that the high frequency suggests that it will experience severe interference from multipath secondary signals reflecting off other objects. VSF-OFCDM is one of the proposed solutions to this problem.

As an IP-based network, 4G will be rolled out using IPv6, which is gradually making its way into telecommunications infrastructure now. In the 4G network, each node will be assigned a 4G-IP address (based on IPv6), which will be formed by a permanent "home" IP address and a dynamic "care-of" address that represents its actual location. For example, say that a device on the Internet, a computer, wants to communicate with a device on a wireless network, a mobile phone. The computer will send a packet to the 4G-IP address of the mobile phone, targeting its home address. A directory server on the mobile phone's home network will forward the packet to the mobile phone's care-of address through a tunnel, mobile IP. The directory server will then also inform the computer of the mobile phone's care-of address (the real location) so it can send subsequent packets directly to the mobile phone.

4G concerns involve cost and the compatibility of various applications, such as three-dimensional virtual reality and interactive video hologram images. 4G will increase interactions between corroborating technologies. For example, the smart card in your telephone will automatically pay for goods as you pass the linked payment kiosk, or the smart card will tell your car to warm up in the morning because your phone has noted you leaving the house or turning off your alarm clock.

Developments for 4G began in 2002, and there are many standards and technologies under consideration, many of which are still in the development stages. Therefore, no one can really say what the future 4G network will look like and what services it will offer. Keep in mind that today's pace of development is so rapid that often a given technology doesn't have a chance to become pervasive in the marketplace before its successor is already named. And that very well may be the case with 3G and 3.5G. Industry visions looking forward may be characterized as involving a horizontal communications model where different access technologies will be combined on a common platform to complement each other in an optimum way for different service requirements and radio environments, possibly including cellular mobile, broadband wireless access, wireless LANs, short-range connectivity, and wired systems.