Patent Application
20080117848
1. Field of the Invention
The invention relates to a communication system, and more particularly, to a power management method using time slots fixed or varied with synchronization frame for reducing total power consumption of the system.
2. Description of the Related Art
One significant goal in communication system design is reduced power consumption. In general, at the circuit level, power consumption can be divided into static and dynamic power consumption. Dynamic power consumption is directly related to the capacitance of load capacitor, operating voltage and operating frequency. Therefore, methods of dynamic voltage and frequency scaling (DVFS) and dynamic frequency scaling are proposed to reduce the power dissipation.
Conventional methods for reducing power consumption are considered at circuit level. One typical method reduces voltage by varying the output of the regulator. However, changing the design of the regulator is not practical and saves minimal power, increasing design cost of the system. Further, one conventional radio frequency (RF) chip can only be switched to a receiving or a transmission mode, failing to reduce power dissipation effectively.
The invention provides a communication system and related power management method thereof. The power consumption is considered at the system level using time slot fixed or varied with synchronization frame to enable or disable related modules. Moreover, techniques which are considered at circuit level, such as DVFS method, can be combined with the invention to further reduce power consumption.
An exemplary embodiment of a method for power management in a communication system is provided. The communication system operates in a first mode and comprises at least one device, wherein the device comprises a first module corresponding to the first mode and is configured to a normal mode or a power saving mode. First, map data is retrieved from frame data, wherein the map data indicates a first time point corresponding to the first mode. Then, the first module of the device is determined to be configured to the normal mode or the power saving mode according to the first time point when the communication system operates in the first mode.
The invention also provides a communication system capable of operating in a first mode. The system comprises at least one device and a power management module. The at least one device comprises a first module corresponding to the first mode wherein the device is configured to a normal mode or a power saving mode. The power management module retrieves map data from frame data, wherein the map data indicates a first time point corresponding to the first mode. When the communication system operates in the first mode, the power management module determines the first module of the device is configured to the normal mode or the power saving mode according to the first time point.
The invention can be more fully understood by reading the subsequent detailed description and examples with reference to the accompanying drawings, wherein:
The following description is one of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The invention provides a method for power management in communication systems capable of performing a time division duplex (TDD) or a half frequency division duplex (H-FDD) protocol. In frame structures of the communication systems, after a mobile station successfully acquires a clear channel for communication, the mobile station uses a dedicated time slot within the frame to transmit (upload) or receive (download) data. The information related to the dedicated time slots for transmitting data and receiving data can be predetermined and thus can be used to control the power state of each module in the communication system. For example, if one of the modules is unnecessary in a specific mode, it can be disabled or shut down. By doing so, all of the modules that are expected to be unused in a specific mode will be disabled and only the necessary modules to perform related operations are enabled such that power consumption is significantly reduced. It is to be understood that the meaning of the term “disable” hereinafter refers to removal of all power from the module or maintenance of only minor power wherein the module itself does not function.
Moreover, each chip in the communication system can be partitioned into several modules in advance according to a usage requirement. According to a given processing sequence, when considered at system level, unnecessary modules can be first disabled, and then enabled at a suitable time point in a specific mode. As a result, power consumption of the system is significantly reduced.
To transmit or receive data, signals with a frame structure are transmitted between the base station 110 and the mobile station 120.
Moreover, the communication system 300 is capable of operating in a receiving mode (i.e. first mode, RX) for receiving data from the base station or operating in a transmission mode (i.e. second mode, TX) for transmitting data to the base station. The RF chip 310, the analog-digital/digital-analog converter 320, the BB chip 330, and the MAC chip 340 within the communication system 300 are partitioned into receiving modules corresponding to the receiving mode and transmission modules corresponding to the transmission mode respectively. For example, the BB chip 330 is partitioned into a receiving module BB_RX that comprises components needed for receiving data and a transmission module BB_TX that comprises components needed for transmitting data. Similarly, the RF chip 310, the analog-digital/digital-analog converter (ADDA) 320 and the MAC chip 340 are respectively partitioned into receiving modules RF_RX, ADDA_RX and MAC_RX, and transmission modules RF_TX, ADDA_TX and MAC_TX. Each or some of the devices (RF/ADDA/BB/MAC chip) may be configured to a normal mode and a power saving mode. When a device is configured to the normal mode, all components within a module are powered up and all functions enabled. When a device is configured in the power saving mode, unnecessary components within a module are disabled, and only necessary components are powered up. In addition, in this embodiment, the analog-digital/digital-analog converter (ADDA) 320, the BB chip 330, the MAC chip 340, the power management module 350, the interrupt handler 360 and the microprocessor 380 may be integrated in a single ASIC chip or integrated together with the RF chip at the same ASIC chip.
The power management module 350 determines whether the devices (RF/ADDA/BB/MAC chip) are configured to the normal (enable) mode or to the power saving (disable) mode. When the communication system 300 operates in the receiving mode, the transmission modules within the devices 310-340 are unnecessary, and thus the power management module 350 configures the transmission modules to the power saving mode. Alternatively, when the communication system 300 operates in the transmission mode, the receiving modules within the devices 310-340 are unnecessary, and thus the power management module 350 configures the receiving modules to the power saving mode. It is to be understood that although the receiving modules or the transmission modules of the devices RF/ADDA/BB/MAC, in this embodiment, are all configured to the normal mode or the power saving mode, the invention is not limited thereto, and can also be applied to control only one or some modules of the device to the normal mode or the power saving mode. Specially, the invention may also be applied in a communication system without a microprocessor or related interrupt handler.
Furthermore, to operate normally, each device requires a special setup time for setting up or warming up the device. For example, the RF chip requires a setup time to await all modules to be ready so that it can be used properly. Therefore, to operate, one module must be enabled before a time interval equals or exceeds its setup time. The setup time of a specific device depends on the system specification, and can be obtained from its data sheet. Thus, the time interval which equals the setup time of the device can be known in advance from its data sheet.
If the period between current time point and the time point TP1 exceeds the predetermined threshold (Yes in step S530), the system will not receive data soon, so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively disabled (step S550). At the same time, a counter can be used to count down from a counter value that equals the period between current time point and the time point TP1. Therefore, it can be used to determine whether the receiving slot is close enough (step S560). If the counter value is not equal to zero, the receiving slot is not close enough yet (No in step S560), so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips respectively remain disabled and the counter value is decreased by one. If the counter value is equal to zero, the receiving slot is close enough (i.e. at an interval prior to the receiving slot) and the system is going to receiving data soon (Yes in step S560), so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively enabled to set up the modules and to prepare to receive data (step S570). Thus, data or user information transmitted from the base station can be received immediately. After an interval subsequent to the receiving slot, the data download is completed, so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively disabled to save power (step S590). It is to be understood that disabling or enabling the modules in steps S510-S590 can be applied to a single module or a plurality of modules.
In a WiMAX system, for example, a communication system receives slot arrangement information from a base station to receive and transmit data by a receiving slot and a transmission slot indicated by map data DL-MAP and UL-MAP assigned by the base station according to present network status. The map data DL-MAP indicates which slot is used for the communication system to receive data, while the map data UL-MAP indicates which slot is used for the communication system to transmit data. It is assumed that the frame data is partitioned into 24 slots SLOT[0] to SLOT[23] in which one half of the 24 slots (SLOT[0] to SLOT[11]) receive data and the other half of which (SLOT[12] to SLOT[23]) transmit data. It is also assumed that the 5th slot SLOT[5] and the 15th slot SLOT[15] are assigned to the receiving slot and transmission slot respectively, and the setup time is about one slot. When the communication system operates in the receiving mode, the transmission modules are unnecessary. Thus, the corresponding transmission modules RF_TX, ADDA_TX, BB_TX and MAC_TX of the RF, ADDA, BB and MAC chips are respectively disabled. Meanwhile, a counter can be used to count down from a counter value that equals 4 and the counter value is decreased by one at each slot. The corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively disabled when the counter value is not equal to zero. When the counter value equals zero, the time point is equal to the 4th slot SLOT[4], so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively enabled, i.e. configured to the normal mode, to set up and initialize the modules. At the time point equalling the 5th slot SLOT[5], the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips respectively are ready so that data transmitted from the base station can be received immediately. After an interval subsequent to the 5th slot, such as the 7th slot SLOT[7], the data download is completed, so the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips are respectively disabled, i.e. configured to the power saving mode. It is to be understood that the corresponding receiving modules RF_RX, ADDA_RX, BB_RX and MAC_RX of the RF, ADDA, BB and MAC chips respectively can be partially or totally disabled once the data download is completed. Similarly, when the communication system operates in the transmission mode, if the time point equals the 14th slot SLOT[14], the corresponding transmission modules RF_TX, ADDA_TX, BB_TX and MAC_TX of the RF, ADDA, BB and MAC chips are respectively enabled, i.e. configured to the normal mode, to set up and initialize the modules. At the time point equalling the 15th slot SLOT[15], i.e. next slot, the corresponding transmission modules RF_TX, ADDA_TX, BB_TX and MAC_TX of the RF, ADDA, BB and MAC chips are respectively ready so that data can be transmitted to the base station immediately. After an interval subsequent to the 15th slot, such as the 17th slot SLOT[17], the data upload is completed, so the corresponding transmission modules RF_TX, ADDA_TX, BB_TX and MAC_TX of the RF, ADDA, BB and MAC chips are respectively disabled, i.e. configured to the power saving mode. It is to be understood that the counter may be countered by units other than slot (such as by time or by data length) used in this embodiment.
Furthermore, properties of other applications, such as a VoIP application, can also be used as reference parameters for power management. One property of a VoIP application, for example, is that next data may not be transmitted until several frames after the current data. In this case, the time for disabling the modules may be extended as much as possible, thereby further reducing the power consumption. Since the data to be transmitted will be put into a transmission queue, it is possible to check the transmission queue first in order to determine whether to enable the related transmission modules of the devices when the communication system operates in the transmission mode.
Additionally, power management of the communication system can also be achieved using interrupt vectors and executing interrupt service routines (ISR) corresponding thereto at specific time points.
The interrupt vectors provide interrupt breakpoints (time point) to determine when to disable or enable the modules. For example, the interrupt vector INT-3 provides an interrupt breakpoint to indicate that the received data has been processed and passed to high layer. In other words, the interrupt vector INT-3 provides the interval subsequent to the receiving slot. Therefore, utilizing specific time points provided by the interrupt vectors, power management in a communication system is enhanced. Detailed process and method for handling or generating interrupt vectors and interrupt service routines corresponding thereto are known to those skilled in the art, and are omitted herefrom for brevity.
While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to the skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
| Number | Date | Country | Kind |
|---|---|---|---|
| TW95142548 | Nov 2006 | TW | national |
