International telecommunication union
Flexible spectrum sharing and cooperative mode identification and monitoring
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- 4.3 Conclusions and perspectives
- 1 Technical aspects
- 1.2 Time slot allocation asymmetry
4.2 Flexible spectrum sharing and cooperative mode identification and monitoringA substantial problem raised by dynamic spectrum sharing is that information on alternative carriers and/or modes varies significantly with respect to time. What is needed, then, are more dynamic methods of collecting and collating information on alternative modes and carriers. A “brute force” approach, of just using the (scarce) gaps in transmit/receive patterns in existing standards, is not only difficult to schedule but is also very resource intensive; such an approach would reduce terminal battery-life to a level not seen for over a decade. A static database orientated system would involve significant overheads due to frequent updates. A measurement of a given carrier in a given mode would, at first glance, appear to be unaffected by which operator was using that carrier. However, as soon as different operators start using that carrier, they would be using their own base-stations, which may well be in different locations to the previous operator’s base-stations, hence affecting the propagation characteristics of that carrier. Cooperative mode monitoring (CoMM) is the idea that, rather than a roaming multi-mode terminal having to (temporarily) reconfigure in order to monitor alternative modes, it is simpler to obtain an idea of coverage in these alternative modes by “asking” terminals that are already operating in that mode for their measurements, or by extrapolating from other measurements taken by terminals in that location. Whether measurements are requested on demand, or are collated centrally over a period of time, will depend on the resultant network loading, and how quickly measurement values “expire”.
Technology solutions to support traffic asymmetry 1 Technical aspectsIn the following, details of the different concepts in § 3.1.2 are summarized. Further details are presented in Recommendation ITU-R M.1036. 1.1 Frequency band asymmetryWith FDD (frequency division duplex) a different amount of uplink and downlink spectrum, separated in the frequency domain, may be allocated for the respective direction. Three cases can be distinguished (typically multiple users share each carrier): – In the first case, the uplink and downlink carrier are of equal bandwidth. However, more carriers are allocated for the downlink compared to the uplink (or vice versa) in order to provide more overall downlink capacity compared to the uplink capacity (or vice versa). – In the second case, the downlink carrier bandwidth is larger than the uplink carrier bandwidth (or vice versa). – In the third case, the same technology is used, in both directions, but well-known multiple access techniques are used to share the uplink carrier while continuing with a dedicated downlink carrier. The above cases require a reasonable a priori estimate of the expected asymmetry for a spectrum efficient frequency allocation and spectrum usage. In order to support flexible asymmetric capacity by means of frequency band asymmetry using the first two methods above, the equipment needs to have the capability for variable duplex distance. With the third method the same carrier bandwidth is used in both directions, but the multiple downlink channels have a common relationship to their own block edge. The lower downlink blocks can provide conventional symmetric operation and some asymmetric operation, while the upper additional downlink blocks with fixed carrier separation to the lower downlink blocks provide support for asymmetric operation (details c.f. Recommendation ITU-R M.1036). Thus the same equipment can be common to all operators. The duplex spacing for equipment using the same blocks is common and instead of variable duplex capability several fixed duplex spacings are required, thus simplifying terminal complexity. Opening up the upper blocks can be timed as additional spectrum and enhanced band equipment becomes available. Note that there is no requirement for the upper blocks to be adjacent to each other. This could be overlaid on “existing” 2G or IMT 2000 technologies, where symmetric bands are already deployed.
A frame comprises N time slots, where n time slots are used for the downlink and N-n time slots are used for the uplink. Another option is to use variable-size time slots rather than multiple time slots. For a TDD system to work properly and achieve good performance a cell should generally avoid having a downlink/uplink configuration different from co-channel or adjacent-channel cells, especially in case of a frequency reuse equal to one to avoid severe interference. However, this can be solved to a large extent if all operators both synchronize their networks and agree on the downlink/uplink configuration in all cells. In the single-operator case and with a frequency reuse larger than one different downlink/uplink configurations in different cells are feasible due to the additional de-coupling by an increased geographical distance between same carrier frequencies. Some degree of frequency planning and coordination would be required. Directory: dms pub -> itu-r -> oth oth -> Section 1a vocabulary, characteristics and general technologies for land mobile service oth -> U. S. Mobile eas for atsc mobile dtv itu-r -> Report itu-r sa. 2312-0 (09/2014) itu-r -> Report itu-r itu-r -> 3rd itu inter-regional workshop on wrc-15 preparation geneva, 1 – 3 September 2015 oth -> Radiocommunication Study Groups oth -> Itu-r workshop on Emergency Broadcasting Speakers Biographies Lynn Claudy oth -> Coordination and notification procedures introduction Download 496.69 Kb. Share with your friends:
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