To address these issues, we are constantly working on the development of the world's leading 3G mobile standard, WCDMA. In this article, I will give a brief summary of the path towards 4G, which goes via the Long Term Evolution standard (LTE), which we expect to be commercially available from 2009.

The first significant step in the evolution of 3G was taken with the software upgrade to HSDPA, High-Speed Downlink Packet Access, launched in 2005 and now being rolled out in 3G networks. HSDPA today offers users 3.6Mbps – very soon to be 7.2Mbps – downlink speeds to their mobile devices and gives operators two to three times more traffic per cell – still within the existing 3G radio spectrum, with the same single 5MHz carrier.

Ericsson led the development of HSDPA; the idea behind the technology was to exploit current radio conditions – in intervals measured in microseconds – for each mobile terminal in a given area, by sending data to the terminal that enjoys the best radio reception at any specific microsecond. The system selects the optimal data bit rates by using link-adaptation technology: in this way, the operator can make the best use of available power by transmitting as much data with as little power as possible.

The second step, which makes High-Speed Packet Access technology complete, is Enhanced Uplink (EUL) – also called HSUPA (High-Speed Uplink Packet Access) –which involves improvements to the link from the terminal to the base station. Enhanced Uplink will be commercially launched this year. Together, the high-speed downlink and enhanced uplink form HSPA.

Initially EUL will provide uplink speeds approaching 1.8Mbps, more than three times the uplink speed of WCDMA networks.

In the near future, EUL will reach 5.8Mbps and the downlink about 14Mbps. This is good enough for most services. Users can now enjoy new experiences by combining images, texts, sounds, video and voice, all sent over the same carrier. The low latency enables interactive applications such as mobile office services or fast internet access, with support for gaming or audio and video downloads. And it also makes broadband services such as video conferencing, e-mail with attachments and file-sharing possible, and convenient.

To evolve HSPA further, a new technology called Multiple-Input Multiple-Output (MIMO) will be introduced. Ericsson is taking part in a number of research projects in this area, some of which are partly financed by the European Union. MIMO uses two or more antennas in the mobile phones and radio base stations. The idea is to raise the transmission speed substantially by sending information over, for example, two parallel data streams, to and from a single terminal, giving roughly double the data rate. Combined with refinements of the modulation – 64QAM (Quadrature Amplitude Modulation) instead of 16QAM – downlink data rates can reach more than 40Mbps on a 5MHz carrier.

But now we are already touching on the next big step: Long Term Evolution. LTE networks can be seen as the bridge between 3G and the 4G of the future, beyond 2010. In fact, LTE has already adopted some 4G features: among these are speeds of 100Mbps, which is a 4G demand.

The LTE standard, which will be ready this year, provides substantially improved performance. This is mainly thanks to a new modulation and transmission technology, Orthogonal Frequency-Division Multiplexing (OFDM), in combination with MIMO. Multi-Layered OFDM, a development of traditional OFDM, is used for the downlink, while the uplink uses SC-FDMA (Single-Carrier FDMA) – an intelligent coding of the OFDM signal that provides much better characteristics in typical mobile applications and reduces power consumption.

Another key benefit is that full-scale LTE will use a much broader carrier, 20MHz (which is variable in bandwidth), giving top speeds of about 100Mbps for the downlink and 25Mbps for the uplink when using two antennas. The latency (roundtrip time) for the signal from a terminal will be as low as 10 milliseconds. All this was demonstrated by Ericsson in a live showcase at this year's 3GSM World Congress in Barcelona .

The launch of LTE is being coordinated with frequency licences and spectrum allocation. LTE will be launched on a number of frequency bands – for example on 2.6GHz, where it will be possible to deploy 20MHz carriers – and it will be used both for existing 3G spectrum and coming broadband carriers. The OFDM technology supports spectrum allocations ranging from 1.25MHz up to 20MHz, and it will be possible to use OFDM in either paired (separate bands for downlink and uplink) or unpaired (same band with time slots) spectrum, since OFDM supports both Frequency-Division Duplex (FDD) and Time-Division Duplex (TDD).

As well as higher peak rates, LTE also provides greater cost efficiency for operators: it is a packet-only network, optimized for high data throughput; incorporates "plug-and-play" and self-configuration concepts; and exploits 3G's economies of scale by using common hardware and software for 3G and LTE. Ericsson 3G base stations delivered since 2005 are all prepared for LTE.

A 3GPP standardization project is developing a new simplified and powerful architecture for core networks, called System Architecture Evolution (SAE). A 3G core network today consists of a circuit-switched part and a packet-switched part. SAE is an evolution of the packet core, where all services will be moved in the long term. In the LTE/SAE network, there will only be two levels of nodes: radio base stations in the access network and "mobile edge" nodes in the core network.

This year, the World Radiocommunication Conference (WRC-07) will identify new frequency bands of 100MHz to be used from around 2015. It will be possible to use the same basic LTE technology on these bands too – allowing Gigabit data rates. IMT Advanced (sometimes called 4G) has been defined by the International Telecommunications Union (ITU) as giving 1Gbps for hotspots and 100Mbps for wide areas and mobile use.

Some people may ask what these tremendous speeds could be used for. What “killer application” could make them worthwhile?

But we are not looking for “killer applications”, but rather a “killer experience”. Users and applications are placing ever-higher demands on data speeds and response times. They want the same speeds on their mobile devices as they get through advanced fixed-line broadband. They will be satisfied with nothing less.

With LTE they should never feel like they have sacrificed anything by “cutting the cord”

--------------------------------------------------------------

 

About the Author

Håkan Eriksson is Senior Vice President and General Manager, Research and Development, and Chief Technology Officer at Telefonaktiebolaget LM Ericsson.

Mr. Eriksson was appointed Senior Vice President and General Manager, Research and Development, and Chief Technology Officer on January 1, 2004.

Mr. Eriksson was appointed Vice President and General Manager for Research and Development at Ericsson on April 14, 2003 , and was responsible for development activities carried out in Ericsson's Core Network Development, Radio Network Development and Service Network and Applications, as well as for Ericsson Research. Prior to this, Mr. Eriksson served for five years as head of Ericsson Research.

Mr. Eriksson joined Ericsson in 1986, representing the company as a technical expert in GSM standardization work and he has held a number of senior positions in the Research and Development field for Ericsson in Sweden and internationally.

Håkan Eriksson was born in Mjölby, Sweden, in 1961. He graduated with a Master of Science degree in Electrical Engineering from Linköping Institute of Technology , Sweden , in 1985.