This is particularly useful in applications in which there is an imbalance in the uplink and downlink, such as video streaming over LTE.
TDD is different from Frequency Division Multiplexing (FDM) used by mobile services today because it uses the same frequency for both transmit and receive paths, making it more spectrally efficient. For example, an FDD band such as PCS Band 25 with a bandwidth of 60MHz, which will utilise a total of 140MHz of bandwidth (1,850-1,915MHz for receive, 1,930-1,995MHz for transmit or a total of 1,995 – 1,850 = 145MHz). Comparatively, TDD (Band 40), which has a bandwidth of 100MHz, will utilise only 100MHz since the transmit and receive paths use the same frequency. To manage this, the DAS are able to detect a downlink burst.
Peter Wraight, President, Wireless business unit, TE, commented: “Spectrum is a scarce commodity and huge investment for mobile operators. It’s important for operators to have access to all frequency bands in order to maximise service to their customers. By supporting TDD-LTE, TE provides a range of new options for mobile operators as they search for spectrum to support their services.”