Sounding reference signals with collisions in asymmetric carrier aggregation
摘要
說明書
Generally, less traffic is transmitted on the uplink than the downlink, so the uplink spectrum allocation may be smaller than the downlink allocation. For example, if 20 Mhz is assigned to the uplink, the downlink may be assigned, e.g., 100 Mhz. These asymmetric FDD assignments may conserve spectrum and may be a good fit for the typically asymmetric bandwidth utilization by broadband subscribers. Therefore, a UE may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation so that it is configured with more downlink CCs than uplink CCs.
Carrier aggregation also provides for use of SRS transmissions. UEs may transmit SRS to base stations, which can be utilized, for example, to determine the uplink channel quality. Base stations can utilize the SRSs in allocating uplink resources to the transmitting terminal. SRS may be used for a variety of actions, such as uplink link adaptation, downlink scheduling under channel reciprocity (especially for TDD systems, coordinated multipoint (COMP) operation, and the like). Certain parameters for transmitting SRSs, such as a maximum transmission bandwidth, available subframes, etc., related to a specific cell, can be defined during operation of a wireless network. Furthermore, UE specific parameters, such as a configuration index of the SRS period and subframe offset for a particular UE, bandwidth for the UE, transmission comb, SRS transmission duration, cyclic shift for generating the reference sequence, and/or the like, can also be defined at runtime. The UE may transmit SRSs as specified by these parameters.
