LTE has been defined to accommodate both paired
spectrum for Frequency Division Duplex, FDD and unpaired spectrum for
Time Division Duplex, TDD operation.
Both LTE TDD and LTE FDD are deployed as each form of the LTE standard has its own advantages and disadvantages and decisions can be made about which format to adopt dependent upon the particular application.
FDD is far more widely implemented because of prior frequency spectrum assignments and earlier technologies.
Yet as spectrum becomes more costly and scarce, TDD will become more widely adopted as spectrum is reallocated and repurposed.
FDD can cover a larger area with the fixed DL/UL on different frequencies, but TDD can provide more DL capacity with the flexible DL/UL ratio.
TDD makes it relatively easy to dynamically change the capacity ratio between UL and DL to reallocate time slots, which makes it well suited for today’s DL-heavy traffic pattern. In most instances, network operators will desire more DL capacity than UL since users more frequently download content like video and web pages than upload content they’ve created.
Not only LTE, but every communication system (except very recent few ones based on full duplexing) requires pairing the transmission and the reception over orthogonal dimensions (frequency or time). Otherwise, the high powered Tx will saturate the neighboring Rx and probably damage it.
That means vendor could combine TDD cell and FDD cell into one base station. Actually most of vendors provide this.
However to choise TDD of FDD depends on business and traffic model. Generally TDD is cheaper than FDD, not only spectrum prices but also equipments price(because the TX&RX antenna could be one， but needs a GPS， so I guess TDD is cheaper than FDD)。Think that FDD have more distant coverages and capacities while TDD is flexible to adjust the ratio of DL/UL，operator like to use TDD as the supplement of FDD. Only seldom operators select TDD alone to build a RAN, most operator select to combine TDD and FDD。
Source : http://goo.gl/T3Elwq
Both LTE TDD and LTE FDD are deployed as each form of the LTE standard has its own advantages and disadvantages and decisions can be made about which format to adopt dependent upon the particular application.
FDD is far more widely implemented because of prior frequency spectrum assignments and earlier technologies.
Yet as spectrum becomes more costly and scarce, TDD will become more widely adopted as spectrum is reallocated and repurposed.
FDD can cover a larger area with the fixed DL/UL on different frequencies, but TDD can provide more DL capacity with the flexible DL/UL ratio.
TDD makes it relatively easy to dynamically change the capacity ratio between UL and DL to reallocate time slots, which makes it well suited for today’s DL-heavy traffic pattern. In most instances, network operators will desire more DL capacity than UL since users more frequently download content like video and web pages than upload content they’ve created.
Not only LTE, but every communication system (except very recent few ones based on full duplexing) requires pairing the transmission and the reception over orthogonal dimensions (frequency or time). Otherwise, the high powered Tx will saturate the neighboring Rx and probably damage it.
That means vendor could combine TDD cell and FDD cell into one base station. Actually most of vendors provide this.
However to choise TDD of FDD depends on business and traffic model. Generally TDD is cheaper than FDD, not only spectrum prices but also equipments price(because the TX&RX antenna could be one， but needs a GPS， so I guess TDD is cheaper than FDD)。Think that FDD have more distant coverages and capacities while TDD is flexible to adjust the ratio of DL/UL，operator like to use TDD as the supplement of FDD. Only seldom operators select TDD alone to build a RAN, most operator select to combine TDD and FDD。
Source : http://goo.gl/T3Elwq
No comments:
Post a Comment