Support of network based positioning by sounding reference signal
A method of network-based positioning using sounding reference signal (SRS) is proposed. An eNodeB configures a number of parameters of a periodic SRS transmission for a user equipment (UE). The eNodeB then transmits SRS configuration data for SRS measurements performed by a location measurement unit (LMU). The SRS configuration data includes cell-specific SRS bandwidth configuration and UE-specific SRS bandwidth configuration. The SRS configuration data may further include a number of antenna ports for SRS transmission, SRS frequency hopping bandwidth configuration, information on whether SRS sequence-group hopping is enabled, and Δ SS when SRS sequence hopping is enabled. Upon receiving the SRS configuration data, the LMU is able to perform timing measurements over the received SRS signals from the UE. In one embodiment, the LMU detects SRS dropping to avoid performance degradation of the network-based positioning.
1. A method comprising:
receiving sounding reference signal (SRS) configuration data transmitted from a base station, wherein the SRS configuration data is used for SRS measurements by a location measurement unit (LMU) for network-based positioning, wherein the SRS configuration data includes cell-specific SRS bandwidth configuration and UE-specific SRS bandwidth configuration, and wherein the SRS configuration data further includes a total number of SRS transmissions for the positioning;
receiving a sounding reference signal transmitted from a user equipment, wherein the sounding reference signal has an SRS sequence, and wherein the SRS transmission is scheduled in specific uplink subframes for reducing SRS dropping based on predefined rules;
detecting an SRS dropping instance using cross-correlation between the SRS sequence and the received signal, wherein the SRS dropping instance is detected when a maximum value of the cross-correlation is below a threshold value; and
performing timing measurements for the received reference signal using the SRS configuration data.
2. The method of claim 1 , wherein the SRS configuration data includes a number of antenna ports for SRS transmission, and wherein the number of antenna ports is set to one for the positioning.
3. The method of claim 1 , wherein the SRS configuration data further includes SRS frequency hopping bandwidth configuration.
4. The method of claim 1 , wherein the SRS configuration data further includes cell-specific information on whether SRS sequence-group hopping is enabled.
5. The method of claim 1 , wherein the SRS configuration data further includes a delta sequence shift ΔSS when SRS sequence hopping is enabled.
6. A location measurement unit (LMU), comprising:
a radio frequency transceiver that receives sounding reference signal (SRS) configuration data transmitted from a base station, wherein the SRS configuration data is used for SRS measurements for network-based positioning, wherein the SRS configuration data includes cell-specific SRS bandwidth configuration and UE-specific SRS bandwidth configuration, wherein the SRS configuration data further includes a total number of SRS transmissions for the positioning, and wherein the RF module also receives a sounding reference signal transmitted from a user equipment, and wherein the SRS transmission is scheduled in specific uplink subframes for reducing SRS dropping based on predefined rules; and
an SRS measurement module that performs timing measurements for the received reference signal using the SRS configuration data, wherein the measurement module also detects an SRS dropping instance using cross-correlation between an SRS sequence of the SRS signal and the received signal, and wherein the SRS dropping instance is detected when a maximum value of the cross-correlation is below a threshold value.
7. The LMU of claim 6 , wherein the SRS configuration data includes a number of antenna ports for SRS transmission, and wherein the number of antenna ports is set to one for the positioning.
8. The LMU of claim 6 , wherein the SRS configuration data further includes SRS frequency hopping bandwidth configuration.
9. The LMU of claim 6 , wherein the SRS configuration data further includes cell-specific information on whether SRS sequence-group hopping is enabled.
10. The LMU of claim 6 , wherein the SRS configuration data further includes a delta sequence shift ΔSS when SRS sequence hopping is enabled.