Telecom-LTE & 3G

Third-generation (3G) wireless systems are deployed all over the world. W-CDMA
maintains a mid-term competitive edge by providing high speed packet access (HSPA) in
both downlink and uplink modes. Typical cell maximum data rate today is around 7.2
Mbps, and typical single-user data rates of around 1.5 Mbps can be expected. To ensure
competitiveness into the future, the long-term evolution (LTE) of the 3rd Generation
Partnership Project’s (3GPP) UMTS is first specified in release 8 of the 3GPP
specification, and covers the emerging needs of “mobile broadband” into the next decade
with cell data rates of over 300 Mbps expected when the system is fully functional.
The majority of work to date on LTE has focused on the frequency division duplex (LTE
FDD) variant. Following the integration of the Chinese TD-SCDMA standard, based on
time division duplex (TDD), into the 3GPP specifications for LTE, chipset and device
designers are now working to include TDD capability. Now known as TD-LTE, the
standard allows carriers to make use of the unpaired spectrum that many of them already
own.


Compared to previous standards such as GSM/EDGE and W-CDMA, the timescale from
first-generation standards documents to commercial release for LTE in general is short,
and for TD-LTE in particular is shorter, due to its later addition into the standards. For
handsets and data cards, LTE’s maximum specified RF bandwidth of 20 MHz has driven
a change in block diagram and the emergence of standard connections, while the
requirement for multi-format devices which include compatibility with legacy systems
may lead designers to the increased use of software-defined radios. New designs need
more analog/digital cross-domain measurement and "digital-in, RF-out", meaning
designers need new tools and measurement methods.
TD-LTE is specified to operate in the frequency range 1850 to 2620 MHz, and uses the
same MIMO scenarios and up- and down-link modulation formats as FDD: OFDMA
(orthogonal frequency division multiple access) in the downlink and SC-FDMA (single
carrier frequency division multiple access) in the uplink.