Jumat, 09 Desember 2011

LTE Frequency Bands & Spectrum Allocations

There is a growing number of LTE frequency bands that are being designated as possibilities for use with LTE. Many of the LTE frequency bands are already in use for other cellular systems, whereas other LTE bands are new and being introduced as other users are re-allocated spectrum elsewhere.

FDD and TDD LTE frequency bands

FDD spectrum requires pair bands, one of the uplink and one for the downlink, and TDD requires a single band as uplink and downlink are on the same frequency but time separated. As a result, there are different LTE band allocations for TDD and FDD. In some cases these bands may overlap, and it is therefore feasible, although unlikely that both TDD and FDD transmissions could be present on a particular LTE frequency band.
The greater likelihood is that a single UE or mobile will need to detect whether a TDD or FDD transmission should be made on a given band. UEs that roam may encounter both types on the same band. They will therefore need to detect what type of transmission is being made on that particular LTE band in its current location.
The different LTE frequency allocations or LTE frequency bands are allocated numbers. Currently the LTE bands between 1 & 22 are for paired spectrum, i.e. FDD, and LTE bands between 33 & 41 are for unpaired spectrum, i.e. TDD.

FDD LTE frequency band allocations

There is a large number of allocations or radio spectrum that has been reserved for FDD, frequency division duplex, LTE use.
The FDDLTE frequency bands are paired to allow simultaneous transmission on two frequencies. The bands also have a sufficient separation to enable the transmitted signals not to unduly impair the receiver performance. If the signals are too close then the receiver may be “blocked” and the sensitivity impaired. The separation must be sufficient to enable the roll-off of the antenna filtering to give sufficient attenuation of the transmitted signal within the receive band.

LTE Band
Main Regions of Use
11920 – 19802110 – 2170Asia, Europe
21850 – 19101930 – 1990Americas, Asia
31710 – 17851805 -1880Americas, Asia, Europe
41710 – 17552110 – 2155Americas
5824 – 849869 – 894Americas
6830 – 840875 – 885Japan
72500 – 25702620 – 2690Asia, Europe
8880 – 915925 – 960Asia, Europe
91749.9 – 1784.91844.9 – 1879.9Japan
101710 – 17702110 – 2170Americas
111427.9 – 1452.91475.9 – 1500.9Japan
12698 – 716728 – 746USA
13777 – 787746 – 756USA
14788 – 798758 – 768USA
17704 – 716734 – 746USA
18815 – 830860 – 875Japan
19830 – 845875 – 890Japan
20832 – 862791 – 821Europe
211447.9 – 1462.91495.5 – 1510.9Japan
223410 – 35003510 – 3600
Note: LTE bands 15 & 16 are reserved, but not yet defined.

TDD LTE frequency band allocations

With the interest in TDD LTE, there are several unpaired frequency allocations that are being prepared for LTR TDD use. The TDD LTE allocations are unpaired because the uplink and downlink share the same frequency, being time multiplexed.

LTE Band
Allocation (MHz)Main Regions of Use
331900 – 1920Asia (not Japan), Europe
342010 – 2025Asia, Europe
351850 – 1910Americas
361930 – 1990Americas
371910 – 1930
382570 – 2620Europe
391880 – 1920China
402300 – 2400Asia, Europe
412496 – 2690USA
There are regular additions to the LTE frequency bands / LTE spectrum allocations as a result of negotiations at the ITU regulatory meetings. These LTE allocations are resulting in part from the digital dividend, and also from the pressure caused by the ever growing need for mobile communications. Many of the new LTE spectrum allocations are relatively small, often 10 – 20MHz in bandwidth, and this is a cause for concern. With LTE-Advanced needing bandwidths of 100 MHz, channel aggregation over a wide set of frequencies many be needed, and this has been recognised as a significant technological problem

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