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JP-7856158-B2 - Control device, control method, and program

JP7856158B2JP 7856158 B2JP7856158 B2JP 7856158B2JP-7856158-B2

Inventors

  • 岩本 真尚
  • 小林 正裕
  • 原田 薫明

Assignees

  • ＮＴＴ株式会社

Dates

Publication Date
20260511
Application Date
20220906

Claims (7)

  1. A control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation unit that estimates whether each carrier is in a sleep state or not based on the traffic load estimated for each carrier, A control device comprising: a calculation unit that calculates a tilt control solution, which is a tilt for each controlled carrier, based on the estimation results by the estimation unit, so as to reduce the power consumption at the plurality of base stations.
  2. The estimation unit estimates the coverage area of each operating carrier, The control device according to claim 1, wherein the calculation unit selects a redundant carrier as the carrier to be controlled, which is a carrier that does not create coverage holes even when the coverage area is excluded.
  3. The control device according to claim 1, wherein the calculation unit calculates the tilt control solution so as to maximize an objective function value that has a value indicating quality degradation as a penalty term, in addition to a value indicating power reduction effect.
  4. The control device according to claim 3, wherein the value indicating the quality degradation is the number of carriers when the traffic load exceeds a threshold.
  5. The control device according to any one of claims 1 to 4, wherein the calculation unit pre-calculates a tilt control solution for each time period based on the estimation results for each time period by the estimation unit, and instructs the control unit to perform control using the tilt control solution corresponding to the time period to which the current time belongs.
  6. A control method performed by a control device in a wireless communication system comprising multiple base stations that autonomously perform sleep control for each carrier, An estimation step to estimate whether each carrier is in a sleep state or not, based on the traffic load estimated for each carrier, A control method comprising: a calculation step of calculating a tilt control solution, which is a tilt for each carrier to be controlled, based on the estimation results from the estimation step, so as to reduce the power consumption at the plurality of base stations.
  7. A program for causing a computer to function as a component of the control device described in any one of claims 1 to 4.

Description

This invention relates to a technology for controlling multiple base stations in a wireless communication system. Base stations in wireless communication systems (which may also be called mobile communication systems) generally have multiple antennas, and each antenna uses a specific frequency band (carrier) to cover an area. Generally, each area is covered by multiple carriers, which allows for the handling of large amounts of traffic. In recent years, efforts to reduce energy consumption have been made in various fields. In wireless communication systems, sleep control technology is being considered to reduce power consumption at base stations by shutting off the carrier (sleeping) at some base stations during times/areas with low traffic demand (Non-Patent Literature 1). Y. Gao, Y. Li, H. Yu, X. Wang and S. Gao, "Energy efficient joint optimization of electric antenna tiltand transmit power in 3GPP LTE-Advanced: A system level result," 2013 IEEE 9th International Colloquium on Signal Processing and its Applications, 2013, pp. 135-139, doi:10.1109/CSPA.2013.6530029. This is a diagram showing the system configuration in an embodiment of the present invention.This is a diagram illustrating the configuration of a base station control unit.This is a flowchart illustrating the operation of the base station control device in Example 1.This is a flowchart illustrating the operation of the base station control device in Example 3.This figure shows an example of the device's hardware configuration. Hereinafter, embodiments of the present invention (this embodiment) will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the embodiments described below. The "antennas and carriers" used by the base station in this embodiment will now be described. The base station consists of multiple antennas, each responsible for communication coverage in a specific direction. The antennas are composed of multiple carriers, and each carrier in a given antenna is responsible for communication coverage in a specific frequency band in the same direction. In this case, a tilt (downward angle) is set for each carrier, and different angles result in different coverage areas. Furthermore, in this embodiment, it is assumed that carriers are classified into two types: "carriers for comprehensively covering each area" (coverage carriers) and "carriers prepared in addition to coverage carriers for areas with high traffic demand" (capacity carriers). However, the technology according to the present invention is also applicable even when carriers are not classified into these two types. The reference names corresponding to the reference numbers (e.g., [2]) referenced in the following explanation are listed together at the end of the specification. Reference [1] is the aforementioned Non-Patent Document 1. In the following, we will first explain the challenges related to power saving and the technology of this embodiment, and then we will explain the technology of this embodiment in detail. In the following explanation, the contents disclosed in the references are publicly known, but explanations other than those disclosed in the references (such as the challenges related to the contents disclosed in the references) are not publicly known. (Regarding power saving) As mentioned above, in wireless communication systems, sleep control technology is being considered to reduce power consumption by shutting off the carrier (putting it to sleep) at some base stations during times/areas with low traffic demand, with the aim of saving power at base stations (Non-Patent Document 1). Sleep control is generally performed autonomously at the base station level in response to traffic load and other factors (Reference [2]). In the technology disclosed in Reference [2], a threshold is set for the traffic load, and sleep is initiated when the traffic load falls below the threshold. This threshold used to determine whether or not to sleep is called the sleep threshold. The range of sleep modes, from largest to smallest, can be: sleep mode for the entire base station including all carriers, sleep mode for individual carriers, and sleep mode for resource blocks (RBs). An RB is a division of a carrier along both the frequency and time axes, and terminals are allocated 2 RB units for communication. Sleep control allows for shorter time intervals compared to tilt control, and switching between each control mode within one second is being considered. When the traffic load on a base station increases, the communication quality of connected terminals may deteriorate. On the other hand, if the traffic load is evenly distributed among the base stations, it is possible that none of the base stations will enter sleep mode because their traffic load will not fall below the sleep threshold. In such a situation, it is difficult to reduce the power con