Can FDD and TDD mode work simulataneously in LTE ?
Is there any possibility of using any other frequency spectrum in LTE like the spectrum used in GSM or WCDMA?
Is there anything like guard band in LTE ?
There is a "Cyclic Prefix" which is used as a gaurd in LTE !
can we use the frequency spectrum 1710-1785 MHZ and 1805-1880 MHZ in LTE ?
Both FDD and TDD modes can work simultaneously in LTE network. Interworking between LTE FDD/TDD in networks will be of increasing importance for operators who have spectrum for both LTE FDD and TDD modes. This allows operators to seamlessly offer mobile broadband services on FDD and TDD spectrum, thus increasing cell capacity and also provide enhanced user experience. Test scenarios with handover between FDD and TDD modes have been demonstrated by some equipment vendors and operators.
GSM/WCDMA spectrum can be used for LTE by spectrum reframing. This is one of the reasons why low bandwidth options like 1.4 MHz have been defined in the LTE specs. It is expected that someday, LTE will operate in those bandwidths used once by GSM/IS-95 and WCDMA systems.
Guard band in LTE is defined as a part of the OFDM definition. For ex., channel BW of 20 MHz will have 100 resource blocks or 1200 usable subcarriers. Therefore transmission BW = 1200*15KHz =18 MHz approximately. Difference between channel BW and transmission BW is considered as guard band ( 20MHz – 18 MHz = 2 MHz). Hence there is no need of separate GB as the energy from the used subcarriers is expected to die down gradually in that 1 MHz space on either end. Similarly, for other bandwidth specifications in LTE, there are guard bands as in the 20 MHz case. Pls refer 3GPP 36.104 section 5.6 for more details on channel BW.