IST-2003-507581 WINNER D2.5 v1.0 Duplex ... - Celtic-Plus

WINNER D2.5 v1.0UL and DL carriers need to be the same, and hence the sizes of the UL and DL bands need not be thesame.TDD does not need a pair of carriers and thus the TDD band can be considered unpaired.2.2.6 Duplex distance (fixed/variable)In FDD the duplex distance is defined as the frequency distance between the center of the UL carrier andthe center of the DL carrier.This distance could be fixed in a system, or it could be variable.2.2.7 Switching pointIn a TDD system, the transceiver switches between a transmitter mode of operation and a receiver modeof operation, or vice versa. Whenever this happens, we have a switching point. Often a basic time period(or frame period) is defined that determines the UL/DL configuration. The more switching points withinsuch a period, the more the UL and DL periods are ‘interspersed’.2.2.8 Activity Profile and Activity factorThe activity profile of a user in the DL defines the time periods where the DL is active. The DL activityfactor is the average time fraction the activity profile is set for DL transmission.The activity profile of a user in the UL defines the time periods where the UL is active. The UL activityfactor is the average time fraction the activity profile is set for UL transmission.If several activity profiles for a link have the same activity factor, the difference between them lies in thelocation of switching points.Example: in a TDD system with a frame structure given by 6 time slots the ‘UUUDDD’ pattern and the‘UDUDUD’ both have UL and DL activity factors 3/6 and 3/6, respectively, but the activity profiles aredifferent due to different switching point locations. The latter pattern enables faster feedback of e.g.control information, but includes several UL/DL switching points (switching times) reducing the spectralefficiency.2.2.9 Duplex asymmetryThe duplex asymmetry measures the basic amount of time-frequency resources in the DL in relation tothe UL. Of course, other characteristics like modulation/coding, interference characteristics, receiversensitivity, power constraints etc., will also impact the capacity of the DL and UL link, respectively, sothe duplex asymmetry as defined above is only partially valid as a measure for the DL/UL capacityrelation. It is however useful as a measure how the ‘natural resources’ time and frequency are expended.In a TDD system, the duplex asymmetry is defined as the ratio of the DL activity factor and the ULactivity factor.In a FDD system, the duplex asymmetry is defined as the ratio between the amount of DL bandwidth andthe amount of UL bandwidth.In a hybrid system using both frequency and time to separate users, the duplex asymmetry is defined asthe product between the FDD duplex asymmetry and the TDD duplex asymmetry as defined above.2.2.10 Guard period (GP)A guard period is an idle time period during which the transmitter and receiver is switched off between aDL transmission and a subsequent UL transmission, or vice versa. For an AP, it might also be the timebetween two subsequent transmission periods to one or more users, or between two subsequent receptionperiods from one or more users.This time is needed in time slot based systems for turning on and off the radio transmitter and receiverhardware and get in a stable mode of operation. Moreover, this time might also be needed for timealignment in larger cells.Page 19 (121)