Dynamic Sampling Frequency Control for Distributed Radio Base Stations
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Solution Overview
Problem
In cellular systems, the existing digital RoF transmission techniques between BBU and RRU result in wasteful band usage due to constant sampling frequencies and quantization bit numbers, even when not all radio bands are allocated to terminals, leading to unnecessary signal transmission and band occupation.
Innovation Solution
Implementing a distributed radio communication base station system that dynamically changes the sampling frequency based on radio band allocation and includes a compression function to stop transmission in unused sections, utilizing optical fiber connections for efficient band utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant sampling frequency and quantization bit number are used in digital RoF transmission, then transmission quality is maintained, but band usage becomes wasteful when not all radio bands are allocated to terminals
Solution Approach 1:
The patent applies dynamics by making the sampling frequency variable rather than constant. The sampling frequency is dynamically adjusted based on the actually allocated radio band width - when fewer resource blocks are allocated to terminals, the sampling frequency is reduced proportionally. This resolves the contradiction by maintaining transmission quality for the actually used bands while reducing band usage waste during periods of low allocation.
Solution Approach 2:
The patent changes the parameter of sampling frequency from a fixed value to a variable value that adapts to the allocation situation. By changing the sampling frequency parameter according to the number of allocated resource blocks, the system maintains reliability for active transmissions while improving band usage efficiency by reducing the sampling rate when fewer bands are in use.
2Device complexity
If fixed data transmission is performed between BBU and RRU, then signal processing is simplified, but unnecessary signal transmission occurs when radio bands are not allocated to terminals
Solution Approach 1:
The patent introduces dynamic control of data transmission between BBU and RRU based on the allocation state of radio bands. When no resource blocks are allocated to terminals, the transmission of IQ data between BBU and RRU is suspended. This dynamic approach maintains simple signal processing architecture while eliminating unnecessary transmissions, thereby improving transmission efficiency without significantly increasing system complexity.
Solution Approach 2:
The system implements feedback mechanisms where the BBU monitors the allocation state of radio bands and controls the transmission of IQ data to the RRU accordingly. When terminals are not allocated any resource blocks, the BBU stops transmitting IQ data, and when allocations are made, transmission resumes. This feedback-based control resolves the contradiction by maintaining simple fixed architecture while dynamically adapting transmission behavior to actual needs.
3Loss of energy
If sampling frequency is reduced to decrease data amount, then band requirement is reduced, but signal quality may deteriorate
Solution Approach 1:
The patent carefully changes the sampling frequency parameter based on the allocated band width, ensuring that the reduced sampling frequency still satisfies the Nyquist criterion for the actually used bandwidth. By proportionally reducing the sampling frequency according to the number of allocated resource blocks, the system reduces band requirements while maintaining signal quality for the active transmissions.
Solution Approach 2:
The patent applies partial action by reducing the sampling frequency only to the extent necessary for the actually allocated bands, rather than reducing it to the minimum possible value. This ensures that the sampling frequency remains sufficient for the active signal bandwidth while avoiding excessive reduction that would compromise signal quality, thus resolving the contradiction between band requirement and signal quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the required band between BBU and RRU, enhances band utilization efficiency, and lowers installation and operation costs by dynamically adjusting sampling frequencies and stopping unnecessary signal transmission.
Implementation Method 1
a radio signal is transmitted between the BBU and the RRU by an RoF technique... Although the RoF technique can be broadly divided into an analog RoF technique and a digital RoF technique
Implementation Method 2
As a transmission medium between the BBU and the RRU, although a coaxial cable, an optical fiber, or the like is used, particularly when the BBU and the RRU are connected through the optical fiber, a transmission distance can be dramatically extended
Data Source
AI summary
Since a sampling frequency of RRU is always constant, A/D conversion may be performed with a sampling frequency higher than necessary with respect to a frequency band width of a radio signal.A sampling frequency change function, and the sampling frequency is reduced in a range where a aliasing component does not deteriorate signal quality of a desired signal component when the sampling frequency is decreased, based on radio band allocation information, or signal transmission between BBU and RRU is stopped in a no signal section, whereby a band required for digital RoF transmission between the BBU and the RRU is reduced.