Method and apparatus for interference control in a multi-cell communication system
AssigneeAmazon Technologies, Inc.
InventorsXiaodong Li, Kemin Li, Titus Lo, Haiming Huang, Jun Meng
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Abstract
Methods and apparatus disclosed maximize the capacity of serving cells and minimize inter-cell interferences due to power emission from serving cells in a multi-carrier, multi-cell communication system. The control methods and apparatus take into account various factors such as cell configuration, frequency reuse, geometry and path-loss information, transmission priority, subchannel configuration, feedback from other cells, or any combination thereof, and produce signals that control the transmission power levels and the modulation and coding of transmitted signals.
Claims18
A method of controlling transmission power of signal transmitters and modulation and coding of transmitted signals in a multi-cell wireless communication system for increasing service capacity of a cell and decreasing inter-cell interference with nearby cells, the method comprising:
- arranging a communication channel into multiple subchannels, wherein each subchannel consists of at least one subcarrier;
- and
- adaptively controlling the modulation and coding of transmitted signals and signal transmission power, wherein the adaptive control is based on rules and constraints derived from system parameters and direct or indirect performance measurements, and wherein a selected transmission power level satisfies a Rise over Thermal (RoT) threshold requirement, and wherein the adaptive control comprises:
- a first process wherein an achievable Channel Quality Information (QNew) at the receiver is updated by:
- Qnew=Qcurrent+Pmax−Pcurrent, where Qcurrent denotes a recent measured CQI (Channel Quality Information) at a receiver, Pmax denotes a maximum transmission power available at a transmitter, and Pcurrent denotes a recent transmission power at the transmitter;
- in a case where a primary criteria is to maximize throughput while controlling transmission power:
- if Qnew exceeds CQI requirement for a highest MCS (modulation and coding scheme) in a protocol, the highest MCS is selected and Pnew is set as the transmission power level for that MCS with a certain margin;
- if Qnew is lower than the CQI requirement for the highest MCS, the maximum transmission power (PNew) is selected to derive a corresponding MCS based on the value of Qnew;
- and
- if Qnew is lower than the CQI requirement for the lowest MCS in the protocol, transmission may be denied and outage process may start;
- in a case where the primary criteria is to minimize transmission power while meeting a data rate requirement:
- if Qnew exceeds the CQI requirement for a given MCS in the protocol, a necessary transmission power level is set for the given MCS with a certain margin;
- and
- if Qnew is lower than the CQI requirement for the given or lowest MCS, transmission is denied;
- and
- a second process wherein an RoT check is performed and, if needed, the power is adjusted to meet the RoT threshold, the second process comprising:
- Rnew=Rcurrent+Pnew−Pcurrent, where Rnew denotes a new RoT resulting from the first process computations, and Rcurrent denotes an RoT measurement before application of Pnew, and wherein:
- if Rnew is less than the RoT threshold, decisions made during the first process concerning the transmission power level and MCS are maintained;
- and
- if Rnew exceeds the RoT threshold, the transmission power level is reduced to meet the RoT threshold requirement;
- and
- a new transmission power level is calculated as:
- Pnew=Pcurrent+Rthreshold−Rcurrent,
- and a new achievable CQI is calculated as:
- Qnew=Pcurrent+Rthreshold−Rcurrent,
- where Rthreshold denotes the RoT threshold and an appropriate MCS is selected based on Qnew.
In a multi-carrier, multi-cell wireless communication system, a process of controlling transmission power of signal transmitters and modulation and coding scheme (MCS) of transmitted signals, the process comprising:
- configuring a communication channel into multiple subchannels, wherein each subchannel consists of at least one subcarrier;
- and
- adaptively controlling the MCS of the transmitted signals and signal transmission powers of the corresponding multiple subchannels to substantially achieve a balance between increasing a capacity of a serving cell and reducing interference with other cells, wherein the adaptive control is based on rules and constraints derived from system parameters and performance measurements, wherein the adaptive control uses the rules to determine the signal transmission powers of the corresponding multiple subchannels at a signal transmitter of the serving cell providing the transmitted signals to a receiver based on interference information received from one or more signal transmitters of other serving cells and representing interference experienced by the one or more signal transmitters of other serving cells providing signals to corresponding receivers in the other serving cells.
In a multi-carrier, multi-cell communication system wherein a communication channel is configured into multiple subchannels and each subchannel includes multiple subcarriers, an apparatus for controlling transmission power and modulation and coding scheme (MCS) of transmitted signals, the apparatus comprising:
- at least one controller configured to process input information and generate output signals for controlling transmission power and the MCS, wherein the controller uses a part or all of the inputs to generate the output signals, and wherein the output signals are sent to and employed by a transmitter in a next transmission, wherein the transmission powers of subchannels provided by the transmitter of a serving cell in the next transmission are based on interference information received from one or more transmitters of other serving cells and representing interference experienced by the one or more transmitters of other serving cells providing signals to corresponding receivers in the other serving cells;
- and
- wherein the input information to the controller comprises:
- performance measurements, wherein the performance measurements are frequently varying and repeatedly updated;
- and
- system parameters and requirements, wherein the system parameters are stable and infrequently updated.
Dependencies are inferred from the claim text.