High-Speed Packet Access (HSPA) is now being rolled out as new software in the 3G network, and the evolved version (HSPA+), with better modulation and multiple antennas (MIMO), is coming soon. And while "real" 4G, as defined by the International Telecoms Union (ITU), is still some way off, the LTE is designed to utilize some of the key components of 4G and make them available on the current 2G and 3G spectrum.

LTE is being developed by the 3GPP (Third Generation Partnership Project) and the standard is expected to be ready in 2007. Top speeds with two antennas per base station and terminal will be 144Mbps (downlink) and 50Mbps (uplink) on a 20MHz carrier; the round-trip time in the radio network is about 10 milliseconds.

Håkan Andersson, responsible for LTE product management, and Mikael Gudmundson, responsible for LTE systems at Ericsson, say the entire network will get a simplified architecture consisting of two nodes, a base station and a core network node (the core network node may be divided into user- and control-plane). Furthermore, the new LTE/SAE (System Architecture Evolution) network will only support the packet domain.

LTE will be launched on a number of frequency bands - for example, on 2.6GHz - which will be licensed in the coming years. When GSM operators' licenses on 900 and 1800MHz start to expire around 2010-2015, there should be LTE products available that suit those frequencies.

LTE will have support for bandwidths ranging from 1.25MHz to 20MHz. The bandwidth used depends on the amount of spectrum available. For example, on the 2.6GHz it will be possible to deploy 20MHz carriers and thereby exploit the full performance of LTE. On frequency bands already used by, for example, GSM, the introduction of LTE should probably be done using a 1.25MHz carrier in the first phase.

Ericsson already has LTE trial systems where data rates of 45Mbps are already being demonstrated, and where data rates exceeding 100Mbps will be shown early 2007.

Much of the planned 4G technology developed in, for example, European research projects, is already being introduced into LTE. As well as higher peak rates, LTE also provides greater cost efficiency for operators, both in terms of being a packet-only network optimized for high data throughput, and by incorporating "plug-and-play" and self-configuration concepts, as well as by riding on the 3G volumes by using common hardware and software for 3G and LTE.