WO2005060358A2

WO2005060358A2 - An apparatus and method for power saving in a subscriber station

Info

Publication number: WO2005060358A2
Application number: PCT/KR2004/002444
Authority: WO
Inventors: Yong-Seouk Choi; Nam-Hoon Park; Jee-Hwan Ahn; Nam Kim
Original assignee: Electronics And Telecommunications Research Institute; Samsung Electronics Co., Ltd.; Kt Corporation; Sk Telecom Co., Ltd.; Ktfreetel Co., Ltd.; Hanaro Telecom, Inc.
Priority date: 2003-12-22
Filing date: 2004-09-23
Publication date: 2005-07-07
Also published as: WO2005060358A3

Abstract

Disclosed is an apparatus and method for saving power of a subscriber station when the subscriber station is accessed by a base station in an initial ranging process. The apparatus and method for saving power of the subscriber station enters a sleep mode for a predetermined period of time when the initial ranging process between the subscriber station and a base station has failed over a predetermined number of times, whereby each time the subscriber station transmits a ranging request signal and scans the reception of a ranging response signal. Upon the first failure of the initial ranging process the said predetermined period of time the sleep mode is maintained is set to a first sleep mode interval and upon the occurrence of a second failure of the initial ranging process the said predetermined period of time the sleep mode is maintained is set to a second sleep mode interval of twice that of the first sleep mode interval. Thereby, the predetermined period of time the sleep mode is maintained is updated exponentially. By turning off the subscriber station during sleep mode the power consumption of the subscriber station is minimized when the initial ranging between the subscriber station and the base station has failed.

Description

Description AN APPARATUS AND METHOD FOR POWER SAVING IN A SUBSCRIBER STATION Technical Field

[1] The present invention relates to an apparatus and method for power saving in a sibscriber station based on the IEEE802.16. More specifically, the present invention relates to an apparatus and method for saving power in a sibscriber station to apply a sleep mode and save the power of the sibscriber station when an initial ranging process has failed. Background Art

[2] In communication environments, the importance of a data service today has been emphasized in a voice-centered mobile communication network. A sibscriber station is convenient for hand-carrying according to the characteristics of mobile communication, and therefore many people use the sibscriber stations, and apparatuses compatible with notebook computer interfaces are tending to be light- weighted.

[3] According to the tendency toward weight reduction, the capacity of batteries installed in the sibscriber stations and notebook computers mist be increased, and a method for efficiently using the power is required for the communication services.

[4] An initial ranging process of the conventional IEEE 820.16 mist be operated by power-on of the sibscriber station or entry into a new cell.

[5] The initial ranging process is a process for controlling time synchronization between the sibscriber station and a base station, a delay according to a gap between each sibscriber station and base station, and controlling RF (Radio Frequency) output power of the sibscriber station.

[6] When the initial ranging process is performed successfully, communication between the sibscriber station and the base station is performed.

[7] The initial ranging process is started when the sibscriber station receives a DL/UL MAP message that is channel assignment information of Downlink/Uplink broadcasted by the base station and a DCD/UCD (Downlink Channel Descriptor/ Uplink Channel Descriptor), comprising information on an assigned channel itself, and it then transmits an RNG (ranging) request signal to the base station based on the above information.

[8] At this time, the sibscriber station mist receive a ranging response signal corresponding to the ranging request previously transmitted, and a succeeding process according to a failure of the initial ranging process is performed when the ranging response signal is not received.

[9] In the succeeding process according to the failure of the initial ranging process, the process in which the sibscriber station increases transmission power at a predetermined rate, transmits the ranging request signal with the increased transmission power, and further increases the transmission power and outputs the ranging signal when the ranging response signal corresponding to the ranging request signal is not received, is repeated.

[10] In the prior art, transmission power is increased gradationally and the initial ranging process is performed continuously when the initial ranging process between the sibscriber station and the base station is performed but has failed, and therefore, power consumption at an earlier stage is problematically increased.

[11] Also, since the transmission of the ranging request signal is repeated several times to execute the initial ranging process again when the initial ranging process has failed, the output is increased at a predetermined rate every time the initial ranging process is repeated, and the initial ranging process is performed repeatedly after a predetermined time for a backoff process to be passed in the case of the continued failures of the initial ranging process.

[12] When the base station fails to receive a signal from the sibscriber station because of the RF interference or the shadow area, or when the sibscriber station fails to receive a signal from the base station, the initial ranging process attempt is repeated until the initial ranging process is performed successfully, and hence, further power is consumed compared to the normal case. Disclosure of Invention Technical Problem

[13] It is an advantage of the present invention to provide a power saving apparatus and method in a sibscriber station for applying a sleep mode, reducing the power consumption of a sibscriber station, and using the power efficiently when an initial ranging process has failed. Technical Solution

[14] The present invention applies the sleep mode for turning off the sibscriber station to save the power of the sibscriber station when the initial ranging process between the sibscriber station and a base station has failed.

[15] In one aspect of the present invention, a method for saving power in a sibscriber station when the sibscriber station is accessed to the base station in an initial ranging process, comprises a) the sibscriber station receiving channel assignment information and channel information assigned by the channel assignment information from the base station when the initial ranging process is performed; b) the sibscriber station transmitting a first ranging request signal and standing by for receiving a response signal to the first ranging request signal from the base station; c) the sibscriber station performing the initial ranging process when the sibscriber station fails to receive the response signal from the base station for a predetermined time; d) the sibscriber applying a sleep mode, entering into an awake mode, and then performing the initial ranging process when the initial ranging process of c) has failed after the initial ranging process is attempted a predetermined number of times; and e) the sibscriber station performing the initial ranging process successfully when the sibscriber station receives the response signal from the base station in c) or d).

[16] It is preferred that d) maintains the sleep mode during a first sleep mode interval and enters into the awake mode; and maintains a second sleep mode interval twice as long as the first sleep mode interval when the initial ranging has failed and a second sleep mode is performed.

[17] It is preferred that d) turns off the internal components of the sibscriber station in the sleep mode condition, and turns on part of the sibscriber station internal components which use the receive sensitivity of the broadcasting signal of the base station to measure a radio environment when the awake mode is performed.

[18] At this time, it is preferred that the internal components of the sibscriber station are turned on to perform the initial ranging process when the radio environment measured by the sibscriber station is above a reference value, all the internal components of the sibscriber station which are turned on are turned off and the sibscriber station enters into the sleep mode when the radio environment measured by the sibscriber station is below the reference value.

[19] In another aspect of the present invention, an apparatus for saving power in a sibscriber station when the sibscriber station is accessed to a base station in an initial ranging process, comprises an RF (radio frequency) processor for processing radio signals transmitted and received by the base station; a modem unit for modulating and demodulating signals input and output by the RF processor; a channel codec unit for performing a coding function and error processing function for respective channels of signal input and output to/from the RF processor; a voice and video codec unit for receiving and processing voice and video signals of users, restoring voice and video data transmitted through the base station and outputting restored data; and a central controller for controlling control functions of the sibscriber station, performing a switching function to a sleep mode and an awake mode according to success or failure of the initial ranging process, and controlling turning on/off operations of the units..

[20] It is preferred that the central controller turns off the RF processor, the modem unit, the channel codec unit, and the voice and video codec unit when the sibscriber station enters the sleep mode; and turns on only the RF processor and a demodulation function of the modem unit, measuring the current radio state when the sibscriber enters into the awake mode from the sleep mode after a predetermined time has passed. Brief Description of the Drawings

[21] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention:

[22] FIG. 1 shows a block diagram of a configuration of an apparatus for saving power in a sibscriber station according to an exemplary embodiment of the present invention;

[23] FIG. 2 shows a flowchart of a method for saving power in a sibscriber station according to an exemplary embodiment of the present invention; and

[24] FIG. 3 shows an example of power-saving according to the performance as shown in FIG. 2. Best Mode for Carrying Out the Invention

[25] In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by way of illustration of the best mode contemplated by the inventor(s) of carrying out the invention. As will be realized, the invention is capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. To clarify the present invention, parts which are not described in the specification are omitted, and parts for which similar descriptions are provided have the same reference numerals.

[26] First, an apparatus for saving power in a sibscriber station according to an exemplary embodiment of the invention will be described with reference to FIG. 1, in detail.

[27] FIG. 1 shows a block diagram of a configuration of the apparatus for saving power in the sibscriber station according to the exemplary embodiment of the present invention.

[28] As shown in FIG. 1, the apparatus for saving power in the sibscriber station according to the exemplary embodiment of the present invention comprises an RF (radio frequency) processor 10, a modem (Modulator/Demodulator) unit 20, a channel codec unit 30, a voice and video codec unit 40, and a central controller 50.

[29] The RF processor 10 transmits and receives radio signals, and the modem unit 20 modulates and demodulates signals that are transmitted and received by the RF processor 10.

[30] The channel codec unit 30 performs a coding function and processes various errors for each channel, and the voice and video codec unit 40 transmits voice and video signals to the central controller 50 when the voice and the video signals are input, and the voice and video code unit 40 restores and then outputs the voice and the video data provided from the central controller 50.

[31] The central controller 50 is a main control board for controlling functions of the sibscriber station, which processes the signals input and output by the modem unit 20 and the voice and video codec unit 40.

[32] An operation of an apparatus for saving power in a sibscriber station according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 2 and FIG. 3.

[33] FIG. 2 shows a flowchart of a method for saving power in the sibscriber station according to the exemplary embodiment of the present invention, and FIG. 3 shows an example of power saving in the sibscriber station according to the exemplary embodiment of the present invention.

[34] As shown in FIG. 2, the sibscriber station (SS) receives DL/UL (Downlink/Uplink) MAP information that is channel assignment information on DL/ UL from a base station (BS) for an initial ranging process.

[35] The base station receives a DCD/UCD (Downlink channel Descriptor/uplink channel Descriptor) comprising channel information assigned to DL/UL MAP information.

[36] The sibscriber station then transmits a ranging request signal (RNG-REQ) that is a first ranging signal to the base station, and stands by for receiving a ranging response signal (RNG-RSP) corresponding to the ranging request signal.

[37] At this time, the sibscriber station successfully performs the initial ranging process when receiving the ranging response signal and it does not repeat the initial ranging process immediately but enters a sleep mode, and then it undergoes an awake mode to thus perform the initial ranging process when the initial ranging process has failed.

[38] It is possible that the base station fails to receive the first ranging signal from the sibscriber station, or the sibscriber station fails to receive the response signal from the base station although the base station has succeeded in receiving the first ranging signal and transmitted the response signal to the sibscriber station.

[39] In that case, when the sibscriber station repeats the initial ranging process, the sibscriber station increases the output and transmits the first ranging signal to the base station. At this time, the base station predetermines the number of times to repeat when the initial ranging process is repeated because of failures of the initial ranging process.

[40] As shown in FIG. 3, when the number of repeated attempts of the initial ranging process is given to be three times and the attempt is performed more than three times by the base station, the sibscriber station determines a rate of successful initial ranging to be low and enters the sleep mode. At this time, a sleep mode interval maintaining the sleep mode is established.

[41] When the sibscriber station is in the sleep mode, the central controller turns off the RF processor 10, the modem unit 20, the channel codec unit 30, and the voice and video codec unit 40 in order to minimize power consumption.

[42] When the sleep mode has expired, the sibscriber station enters the awake mode, turns on the RF processor 10 and a demodulator of the modem unit 20, and scans whether the sibscriber station receives the DL/UL MAP signal comprising the DL/UL channel assignment information broadcasted by the base station.

[43] At this time, the sibscriber station turns on a modulator of the modem unit 20 and transmits the first ranging request signal when the DL/UL MAP signal is received properly, and the sibscriber station turns off the RF processor 10 and the demodulator of the modem unit 20 which are turned on and returns to the sleep mode when the DL/ UL MAP signal is received inadequately.

[44] Also, the initial ranging process is performed a predetermined number of times in the above case. If the initial ranging process fails to be performed successfully in a predetermined number of times, the sibscriber station returns to the sleep mode.

[45] When the sibscriber station enters the sleep mode for the second time, the sibscriber station increases the sleep mode interval to twice the previous sleep mode interval and returns to the sleep mode.

[46] The reason why the sleep mode interval is doubled upon at least two entries into the sleep mode is to prevent the power consumption according to the low probability of success of the initial ranging process in the present radio environment. [47] When the turned-off sibscriber station is switched to be turned on or enters a new cell so as to perform the initial ranging process, it is not possible for the initial ranging process to be performed successfully in the RF interfered area or the shadow area. Therefore, the power consumption is minimized in the sleep mode.

[48] When the sleep mode is finished, not every system of the sibscriber station is turned on, but the RF processor 10 and the demodulator of the modem unit 20 are turned on to measure the present RF environment using receive sensitivity of broadcasting signals by the base station which is on the downlink.

[49] At this time, when the radio environment is above a reference value, other parts of the sibscriber station, that is, the modulator of the modem unit, the channel codec unit 30, and the voice and video codec unit 40, are turned on to perform the initial ranging process. However, when the radio environment is below the reference value, the sibscriber station turns off the RF processor 10 and the demodulator which are turned on and enters the sleep mode.

[50] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[51]

[52]

Claims

[1] A method for saving power in a sibscriber station when the sibscriber station is accessed to a base station in an initial ranging process, comprising: a) the sibscriber station receiving channel assignment information and channel information assigned by the channel assignment information from the base station when the initial ranging process is performed; b) the sibscriber station transmitting a first ranging request signal and standing by for receiving a response signal to the first ranging request signal from the base station; c) the sibscriber station performing the initial ranging process when the sibscriber station fails to receive the response signal from the base station for a predetermined time; d) the sibscriber applying a sleep mode, entering an awake mode, and then performing the initial ranging process when the initial ranging process of c) has failed after the initial ranging process is attempted a predetermined number of times; and e) the sibscriber station performing the initial ranging process successfully when the sibscriber station receives the response signal from the base station in c) or ).

[2] The method of claim 1, wherein c) and d) comprise increasing the output of a first ranging signal and performing the initial ranging process a predetermined number of times.

[3] The method of claim 1, wherein d) comprises maintaining the sleep mode during a first sleep mode interval and entering an awake mode, and maintaining a second sleep mode interval twice as long as the first sleep mode interval when the initial ranging has failed and a second sleep mode is performed.

[4] The method of claim 1, wherein d) comprises turning off the internal components of the sibscriber station in the sleep mode condition, and turning on part of the sibscriber station internal components which use the receive sensitivity of the broadcasting signal of the base station to measure a radio environment when the awake mode is performed.

[5] The method of claim 4, wherein the internal components of the sibscriber station are turned on to perform the initial ranging process when the radio environment measured by the sibscriber station is above a reference value, and the internal components of the sibscriber station which are turned on are turned off and the sibscriber station enters into the sleep mode when the radio environment measured by the sibscriber station is below the reference value.

[6] An apparatus for saving power in a sibscriber station when the sibscriber station is accessed to a base station in a process of an initial ranging process, comprising: an RF (radio frequency) processor for processing radio signals transmitted and received by the base station; a modem unit for modulating and demodulating signals input and output by the RF processor; a channel codec unit for performing a coding function and an error processing junction for respective channels of signals input and output to/from the RF processor; a voice and video codec unit for receiving and processing voice and video signals, restoring voice and video data transmitted through the base station, and utputting restored data; a central controller for controlling control functions of the sibscriber station, performing a switching function to a sleep mode and an awake mode according to success or failure of the initial ranging process, and controlling turning on/off operations of the units.

[7] The apparatus of claim 6, wherein the central controller turns off the RF processor, the modem unit, the channel codec unit, and the voice and video codec unit when the sibscriber enters the sleep mode.

[8] The apparatus of claim 7, wherein the central controller turns on the RF processor and a demodulation function of the modem unit, measuring the current radio state when the sibscriber station enters into the awake mode from the sleep mode after a predetermined time has passed.

[9] The apparatus of claim 8, wherein the central controller turns on a modulation iunction of the modem unit, the channel codec unit, and the voice and video codec unit and performs the initial ranging process when the signals from the base station are properly received as a result of estimating the radio environment; and the central controller turns off the RF processor and the demodulation iunction of the modem unit and switches into the sleep mode when the signals from the base station are inadequately received.