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LTE

Long Term Evolution (LTE), is a new radio platform technology with standards completed in March 2009 in 3GPP Release 8. Trials are planned for 2009 with initial deployments in 2010 to 2011. LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink, which is well-suited to achieve high peak data rates in high spectrum bandwidth. LTE is part of the GSM evolutionary path beyond third generation (3G) technology, following EDGE, UMTS, HSPA (HSDPA and HSUPA combined) and HSPA Evolution (HSPA+). In the same way that 3G coexists with second generation (2G) systems in integrated networks, LTE systems will coexist with 3G systems as well as 2G systems. Multimode devices will function across LTE/3G or even LTE/3G/2G, depending on market circumstances.

What is LTE expected to provide?

  1. Downlink peak data rates up to 326 Mbps using 20 MHz spectrum channels and 4x4 MIMO
  2. Uplink peak data rates up to 86 Mbps using 20 MHz spectrum channels and 64 QAM
  3. Operation in both FDD and TDD modes
  4. Scalable bandwidth up to 20 MHz, covering 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz (1.6 MHz channels are under consideration for unpaired frequency bands)
  5. An increase in spectral efficiency of two to four times that of HSPA Release 6
  6. Reduced latency to 10 milliseconds (ms) round-trip time between user equipment and the base station and to less than 100 ms transition time from inactive to active
  7. LTE will address the market needs of at least the next decade, after which time operators might deploy Fourth Generation (4G) networks using LTE-Advanced technology as a foundation.

Where does LTE lie in the GSM evolutionary path?

Although HSPA and HSPA Evolved (HSPA+) are strongly positioned to be the dominant mobile data technologies for the rest of the decade, it is important to evolve the GSM family of standards toward the future. HSPA+ will provide the stepping-stone to LTE for many operators.

It is recognized that many comments have been made by people throughout the wireless ecosystem, including members of the press, the vendor and operator communities, as well as the analyst community, identifying LTE and even WiMAX as “4G” technologies. While 3G Americas acknowledges that these technologies, incorporating OFDMA, will be the next evolution of wireless mobile technology after 3G, the organization does not consider them to be 4G technologies. Because the International Telecommunication Union (ITU) has not yet finished its IMT-Advanced “4G” development process, it is the position of 3G Americas that neither WiMAX, LTE, nor any other technology can officially be called “4G” at this point in time. However, LTE based on OFDM technology will provide significant performance improvements over 3G technologies in large spectrum swaths and work has already commenced in 3GPP Release 10 on the development of an IMT-Advanced standard, now called LTE-Advanced.

What is OFDM and how is it related to LTE?

Orthogonal Frequency Division Multiplex (OFDM) is a modulation technique suitable for high data rate communication. OFDM techniques are popular in wireless communications and they form the base technology for standards such as WiMAX IEEE 802.11a/b/g, 802.16e/m. It is also found in the more general broadcasting world of Digital Video Broadcast (DVB) and Digital Audio Broadcast (DAB). OFDM was selected to be used in LTE downlink in December 2005 by 3GPP.


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