Ericsson: LTE tech in brief

Background
In just a few years more people will have access to mobile broadband than fixed – and most of these will be served by LTE networks.

LTE was introduced in 3GPP Release 8, and compared to 2G or earlier 3G technologies, LTE provides a superior user experience and supports demanding applications, such as interactive TV, user-generated videos, and advanced gaming.

In addition to LTE, the 3rd Generation Partnership Project (3GPP) has specified a flat IP-based network architecture as part of the System Architecture Evolution (SAE) effort. The aim of the LTE-SAE architecture is to efficiently support mass-market usage of any IP-based service. The architecture is based on existing GSM/WCDMA core networks, and one of its targets is to reduce operating expenses (opex) and capital expenditures (capex). To that end, LTE-SAE supports a high degree of automatic network configuration.

The starting point for LTE standardization was the 3GPP RAN Evolution Workshop, held in November 2004 in Toronto, Canada. Later the same year, a study item was initiated with the objective to develop a framework for the evolution of the 3GPP radio access technology towards qualities such as reduced cost per bit; improved service provisioning; flexible use of existing and new frequency bands; simplified architecture and open interfaces; and reasonable terminal power consumption.

LTE overall performance
Notable examples of improved performance compared with early 3G systems include peak data rates in excess of 300Mbps, delay and latencies of less than 10ms, and manifold gains in spectrum efficiency. With LTE the target is to provide data rates of at least 100 Mbps in the downlink and at least 50 Mbps in the uplink on a 20 MHz carrier.

LTE can be deployed both in new and existing frequency bands, and it facilitates simple operation and maintenance. In addition, LTE both targets smooth evolution from legacy 3GPP and 3GPP2 systems and constitutes a major step toward IMT-Advanced (International Mobile Telecommunication – Advanced, sometimes referred to as 4G). In fact, LTE includes many of the features originally considered for a future 4G system.

Key LTE radio access features
LTE uses orthogonal frequency division multiplexing (OFDM), with data transmitted over several parallel narrowband subcarriers, for the downlink radio transmission. This simplifies receiver baseband processing and thus reduces terminal cost and power consumption.

In the uplink one of the most important factors is a power-efficient transmission scheme, used in order to maximize coverage and lower terminal cost and power consumption. Consequently, the LTE uplink employs single-carrier transmission in the form of DFT-spread OFDM (also called single-carrier FDMA). This solution has a smaller peak-to-average-power ratio than regular OFDM, resulting in more power-efficient and less complex terminals.

One of main features of LTE is spectrum flexibility. LTE can be deployed with bandwidths ranging from 1.4MHz up to 20MHz. Furthermore, it can operate in both paired and unpaired spectrum by providing a single radio-access technology that supports frequency division duplex (FDD) as well as time division duplex (TDD) operation.

To yield good performance over a broad range of scenarios, LTE uses advanced antenna solutions exploiting diversity, multi-layer transmission and beam forming.

To summarize, LTE supports high throughput; low latency; plug and play from day one; FDD and TDD in the same platform; superior end-user experience; and simple architecture resulting in low opex.

Terminals, modules and fixed wireless terminals
LTE will be available not only in next generation mobile phones but also in notebooks, ultra-portables, cameras, camcorders, Fixed Wireless Terminals and other devices that benefit from mobile broadband.

LTSI and NGMN
The LTE/SAE Trial Initiative (LSTI) is a group of leading telecom operators and suppliers (including Ericsson) working with LTE proof-of-concept, interoperability and trials, as well as LTE promotion.

The Next Generation Mobile Network (NGMN) group has selected LTE as its main next generation network candidate.

LTE spectrum
UHF spectrum (700 – 800) was freed for LTE in 2008. In the 2009/2010 time frame, the focus will be on frequency bands in the 2.6 GHz range.

See also:
General LTE information on the 3GPP home page
…and on the Global mobile Suppliers Association (GSA) home page