MXPA06007169A - Precise sleep timer using a low-cost and low-accuracy clock - Google Patents

Abstract

A wireless transmit/receive unit (WTRU) uses an oscillator providing accuracy for synchronized communications parameters in an active mode, and operates at reduced power during a discontinuous reception (DRX) mode. A real time clock (RTC) is used as the frequency standard during the reduced power operation, and a frequency adjustment is effected while the RTC is used as the frequency standard. By effecting the frequency adjustment, the RTC is able to be used as the frequency standard for substantial time periods, thereby reducing power consumption of the WTRU during the DRX mode.

Description

WO 2005/062855 A2! Llll] llllllllllllllllllllllllllllllllllllllll European (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, For two-letler codes and other abbreviations.) Refer to the "GuidFR, GB, GR, HU, IE, IS, IT , LT, LU, MC, NL, PL, PT, RO, ance Notes on Codes and Abbrevialions "appearing at the begin- SE, SI, SK, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, no regular issue of the PCTGazeite, GQ, GW, ML, MR, NE, SN, TD, TG). Published: - without inlemational search report and it is republished upon receipi ofihat repon PRECISE OFF TIMER USING A LOW COST CLOCK AND LOW ACCURACY FIELD OF THE INVENTION The present invention relates to reference oscillators for wireless communication devices, and, more particularly, to the power consumption control of such reference oscillators.

BACKGROUND There are algorithms that calibrate a low precision clock with respect to a high accuracy clock, which is also referred to as a master clock. This allows a low precision clock to produce a timing with almost as much precision as the master clock. These techniques have one thing in common: calibrate the low precision clock periodically with respect to a master clock. In battery-operated devices, such as wireless transmission / reception units (WTRUs) and other mobile devices, it is very important to limit the consumption of electrical power to prolong the battery life. The algorithms and hardware in the WTRU should be designed to minimize the consumption of electrical power. The life of the battery can also be extended by reducing the power consumption during periods of • inactivity where certain functions can be disabled or operated in some form of reduced power mode. The UMTS is configured so that a WTRU can operate with reduced functions during periods of inactivity. The WTRU only occasionally needs to perform certain functions to maintain synchronization and communications with its associated base station while a call or other dedicated connection is not in progress providing the periods of inactivity that may allow the WTRU to minimize its power consumption electric This is achieved through the WTRU that operates using discontinuous reception (DRX), where the WTKJ periodically cycles between "inactive" and "activation" periods. During inactive periods, hardware and non-necessary procedures that consume full power torque are disabled. During activation periods, these procedures and hardware, necessary to preserve synchronization and communications with the associated base station, are momentarily re-enabled. Currently, most portable WTRUs include a low precision real time clock (RTC) in addition to the high precision master clock. The master clock is typically implemented using a temperature controlled crystal oscillator (TCXO). The RTC typically consumes much less power than a TCXO, which makes it convenient to use the RTC instead of the TCXO to provide timing functions during DRX.

However, there are four problems related to the use of an RTC for timing functions during DRX. First, the RTC typically operates at a very low speed compared to the TCXO (eg, 32,768 KHz vs. 76.8 MHz). Secondly, the frequency accuracy of the RTC may be very low compared to the one of a TCXO. Third, the frequency drift of the RTC, due to different environmental reasons, such as temperature changes, may be greater than that of a TCXO. Fourth, the RTC typically operates asynchronously to the TCXO. For these reasons, a typical RTC is, by itself, inadequate to provide timing functions during DRX.

THE INVENTION A WTRU includes a high stability reference oscillator, high accuracy, high speed and high power consumption, such as a TCXO and a lower stability RTC, lower accuracy, lower speed and lower power consumption. The TCXO nominally provides timing functions for the WTRU. The RTC itself may not provide timing functions accurate and accurate enough for the WTRU. To minimize power consumption during operation, using discontinuous I A reception (DRX), the TCXO shuts off periodically, during which time the RTC provides timing functions for the WTRU. A calibration and synchronization method between the TCXO and the RTC ensures that the timing functions provided by the RTC during DRX are sufficiently precise and accurate. '' BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the operation of a WTRU in active operation modes 11 and DRX 12. Figure 2 is a block diagram of input and output signals used by a timer algorithm. of inactivity. Figure 3 is a block diagram showing the interaction of the inactivity timer with the other receiver synchronization algorithms. Figure 4 is a time diagram for the processing of Layer 1. * Figure 5 is a diagram of an RTC frequency estimation window. Figure 6 is a time diagram for cases of inactivity timer programming. Figure 7 is a flow chart for the procedures for closing the oscillator during DRX. < * DETAILED DESCRIPTION OF THE PREFERRED MODALITIES As used herein, the term "wireless transmit / receive unit" (WTRU) includes, but is not limited to, a user equipment, a mobile station, a fixed subscriber unit. or mobile, a pager, or any other type of device capable of operating in a wireless environment. The term "base station" includes, but is not limited to, a Node B, a site controller, an access point or any other type of interface device in a wireless environment. Although some MODALITIES are explained together with the third generation collaboration program system (3GPP), they are applicable to other wireless systems. In accordance with the present invention, a high-power, high-accuracy oscillator is turned off during an idle mode and an alternate low-power and low-accuracy oscillator is used, combined with an inactivity timer algorithm. Using the low power oscillator can achieve a longer battery life. Typically, the low-power, low-accuracy oscillator operates in orders of magnitude of a lower frequency than the high-power, high-accuracy oscillator. For example, in an exemplary embodiment, an RTC used as a low-power clock operates in the industry standard of 32,768 KHz. The RTC operates at a reduced speed compared to the high-power, high-accuracy oscillator. While the use of an RTC is common in portable WTRUs, this modality provides an ability to use the RTC peer * idle mode operations. * An off timer (ST) e's algorithm used to implement the DRX timing and allows the main TCXO to be turned off. To reduce the power consumption of the WTRU in the standby state, the TCXO can be closed during the idle periods of the DRX. When the TCXO is turned off, an RTC or a low-power crystal oscillator is used to control the DRX timing until the power of the TCXO rises again. For such purpose, a real-time clock based on industrial standard quartz crystal or another standard clock circuit is used as an RTC. The RTC is combined with an inactivity timer algorithm, which overcomes the problems of using the RTC in the mo or DRX. The use of an inactivity timer algorithm solves these two problems, applying programming and frequency measurement. The RTC can. be any clock or oscillator suitable. This does not change the algorithm; only its parameters. The application of the invention is described in the context of the DRX, which is explicitly provided in the UMTS standard. However, the invention may work for a WTRU having an inactive mode independent of the standards, for example, one mode for the DRX and another mode for an inactive period not based on standards. Figure 1 is a flow chart showing the operation of a WTRU in active operation modes 11 and DRX 12. In active mode 11, the WTRU provides complete communication functions, represented by the communication device 13. While there is modes of power saving during portions of communication frames, in general, the WTRU is synchronized by a synchronization device 14 and a timing by a timing device 15 in full operation, actively using the TCXO 17. The RTC function, as it is carried out by the RTC device 18, may be operating, but the communications device 13 depends mainly on TCXO 17. * When the WTRU is in the DRX 12 mode, the synchronization and timing functions are present, as illustrated for the synchronization device 24 and the timing device 25, but at a reduced level. The WTRU must be able to recognize a case that requires an active mode of operation, and preserve communications by means of a communication device 23 to a limited degree. This is achieved with a reduced timing and synchronization capacity. This reduces the need for use of the TCXO 27, and makes it possible to rely on the RTC 28. Figure 1 represents different modes of operation of the same device, and thus the physical components of the illustratively different TCXOs 17, 27 and the RTCs 18 , 28 are carried out by the same physical devices. i Operations performed during inactivp mode include searching for the location channel, performing cell reselection measurements, and verifying user activity. If there is a location, the WTRU leaves the inactive mode and enters the active mode as it will be described. ' The inactivity timer is able to control its DRX and active components and enters synchronization update, according to an algorithm. The inactivity timer algorithm includes an active cycle component, generally compatible with the active cycle operation and a DRX component and compatible with DRX operation. In the active cycle, the active cycle component retains the operation under the TCXO and retains an ability to transfer operation to the RTC. The active cycle component includes a sync update, and a determination as to whether the WTRU should enter the DRX mode. This determination as to whether the WTRU should enter the DRX mode is performed according to predetermined inactivity criteria. Examples of criteria for entering DRX mode include ending a conversation, inactivity for a predetermined period of time, a predetermined time period of cell search activity without locating an appropriate signal and a predetermined number of consecutive cell search attempts. not successful The specific criteria are a function of the WTRU. In a particular embodiment, a RTC frequency measurement is carried out. However, the RTC frequency measurement can be avoided since it can be carried out in the DRX component. The WTRU enters the DRX mode when a period of relative inactivity is identified by the WTRU after a determination. In the DRX component, a measurement of the RTC frequency is carried out on a periodic basis to preserve the synchronization, and a determination is made as to returning to the active mode. The components of Figures 3 and 4 can be implemented using an integrated circuit, such as a specific application integrated circuit (ASIC), multiple ICs, discrete components, or a combination of IC (s) and discrete components. Figure 2 is a block diagram of input and output signals used by the idle timer algorithm 80. The master clock and the DRX Cycle Length are the inputs to obtain a frequency measurement of RTC 83. The calculations 88 are then executed for activation and inactivation locations, which, in turn, are used to generate activation times 93. The TCXO Power Increase, the TCXO Power Decrease and the next location occasion (PO) are the outputs of the Algorithm 80. - * The inactivity timer interaction c? The other algorithms of the receiver are shown as a blog diagram in Figure 3. The inactivity timer is controlled by itself according to the inactivity timer procedure which is described below. The block diagram of Figure 3 shows the interaction of the inactivity timer with the other receiver synchronization procedure. The components include a timing manager 111, an ADC circuit 112, an AGC circuit 113-, a reception filter circuit 114, a frequency estimation circuit 115, a loop filter 116, a digital-to-analog converter (DAC) 117 and a TCXO 118. they also show a cie timing correction circuit. frame (FTC) 121, and a master clock 126, an RTC 127 and an inactivity timer 128. This circuit implements an algorithm responsible for acquiring and conserving the frame synchronization of the receiver. The ADC circuit 112, the AGC circuit 113, a reception filter circuit 114, a frequency estimation circuit 115, a loop filter 116, a DAC 117 and a TCXO 118 form a frequency estimation loop 131. The manager of timing 111, circuit ADC 112, circuit AGC 113, a receiver filter circuit 114 and an FTC circuit 121 provide a frame synchronization loop 132. In this particular embodiment, the inactivity timer 128 receives signals from the clock teacher 126 and the RTC 127, which in turn, provides signals to turn on and off the TCXO 118. The entries are as follows: 1) Master clock (MC), like the one with a nominal frequency of 76.8 MHz (chip frequency 20X); and 2) RTC, as being with a nominal frequency of 32,768 Hz. The control aspects are as follows: 1) DRX Cycle Length in terms of frames is provided as an input to the algorithm; 2) Next Case is a binary entry that is either a Location Block or a Sync Update Block; and 3) Starting PO is the first MC pulse of a PO. The outputs are as follows: 1) TCXO Power Decrease indicates when TCXO power should be turned off; 2) Power Increase of TCXO indicates the power increase time of the TCXO in terms of RTC pulses; and 3) Update position sync or PO Next: depending on the location block considered, the following activation time can be either a PO or a sync update period. This output shows the beginning of these cases in terms of MC pulses (20X chip frequency). The operations executed during the inactive mode consist of searching the localization channel, carrying out cell reselection measurements and verifying the user's activity. If there is a location, the WTRU leaves the inactive mode and enters the active mode. Cell reselection is a continuous procedure of measuring the most intense cell at any given time, during location blocks, as shown in Figure 4. Figure 4 is a time diagram for processing layer 1 in the DRX mode. The inactivity timer works during the DRX cycles. The algorithm has two different parts that work at different speeds -, -. The first part is the frequency measurement of RTC. This part of the algorithm operates during each sync update period, which is shown in Figure 4. Frequency measurement also operates just before the WTRU enters the DRX cycle. The second part of the algorithm is responsible for indicating the position of Update sync or PO. This part operates for each PO during DRX cycles. This two-part algorithm is considered as a very efficient algorithm in terms of computation, although other algorithms can be used. In the particular example shown in the diagram, a frame offset is followed by a synchronization update period, which is followed by a sync update block 164. A series of location blocks 171 through 174. are shown. various pre-heating periods RX 181 to 183, which usually precede other activities, such as location blocks 172, 173 or update block sync 164. Inactive periods, such as inactive period 191, precede pre-heating periods RX 181 a 183. The synchronization update period 162 precedes the sync update block 164. RX_Preheating is a parameter that is used to turn on the TCXO approximately 5 msec before to allow pre-heating of the TCXO. It is approximately equal to the number of MC pulses (20x) in 5 msec. The number in this mode is set at 384,000. The purpose of the DRX is to identify periods of relative inactivity, which provide opportunities to conserve battery power by decreasing the power of various components included in the WTRU and becoming "inactive". The WTRU receives information on occasions when it must be activated in order to receive transport information. The DRX is used in standby mode and in the states CELL_PCH and URA_PCH connected mode. During DRX, the WTRU must be activated in POs, as ordered by the RRC (Radio Resource Controller) based on system information configurations. A PO indicates the beginning of a Location Block. The RRC is responsible for programming when, for how long and in what channel Layer 1 should pay attention to each of these procedures. The time difference between two POs for a specific WTRU is called the DRX cycle length. A PO corresponds to a location block. A location block consists of several frames and contains: 1) a location indicator channel block (PICH) consisting of 2 or 4 frames of Location Indicators (PIs); 2) a separation period consisting of 2, 4 or 8 frames where physical resources can be used by other channels; and 3) location channel block (PCH) which consists of 2 to 16 frames of location messages for between one and eight location groups. When using DRX, a given WTRU needs only to monitor one PI in one PO for each DRX cycle. The timing diagram of the Location Blocks is shown in Figure 4. The DRX cycle lengths can vary between 8 and 512 frames, such as in the standby mode, and the possible DRx cycle lengths are 0.64, 1.28, 2.56 and 5.12 seconds; and in states CELL / URA_PCH, the possible DRX cycle lengths are 0.08, 0.16, 0.32, 0.64, 1.28, 2.56 and 5.12 seconds. The WTRU should update its timing and frame synchronization periodically during DRX to be able to read the PIs and perform cell reselection measurements successfully. Therefore, periodic DRX activities for Layer 1 include cell reselection and related measurements, monitor PIs; and conservation of timing and frame synchronization.

If the WTRU detects that it is located through the related PI, it reads the PCH to access the location message. Otherwise, it returns to the inactive state. If the TCXO runs continuously, it will draw a maximum current of 2.0 mA from a nominal DC power supply of 3.0 V or 6.0 mWatts of power. For additional power savings, the TCXO can be closed during inactive DRX periods. When the TCXO is turned off, the inactivity timer is used to program activation times for the TCXO for the POs or the start of the sync update periods d_e. The power consumption of the RTC is typically negligible compared to the TCXO, in the order of 1 microamp of a 3 V or 3 microwatts DC power supply. There are three problems associated with the use of the RTC. First, the RTC resolution does not meet the requirements of some wireless systems, such as bandwidth code division multiple access time division duplex (TDD) mode (WCDMA). The frequency - typical of the RTC is 32,768 Hz. This corresponds to a minimum resolution of 30.52 microseconds or 117.19 chips or 2,343.8 of 20X samples (76.8 MHz). The second problem is the frequency accuracy of the RTC. The operating frequency of. RTC may be different from the nominal frequency up to a maximum deviation of 100 ppm. Third, the frequency stability of the RTC may be low. For this problem, it is assumed that the drift velocity will not be greater than [+/-] 0.3 ppm per minute or 0.005 ppm per second. This speed is typically the worst case for a room-temperature crystal oscillator (RTXO), which uses a cut-off glass or specifically for a lower sensitivity to temperature. Since these oscillators do not have special cabinets as in the case with the TCXO, they have a lower cost. The inactivity timer algorithm consists of two parts: the frequency measurement of the PSTN and the programming of the inactivity timer. The frequency measurement is carried out periodically during the DRX cycles to overcome the problems of frequency accuracy and frequency stability .. The programming part meets the resolution requirements of the WTRU to accurately program DRX cases when switched off the TCXO. Frequency correction is not necessary for the RTC. It is only necessary to accurately measure the frequency of the RTC. There is no need to carry out frequency measurement in the active connected mode, since the TCXO is ON all the time. The RTC frequency measurement is required just before entering the DRX cycles and during the DRX. The update rate should be such that the total frequency accuracy should be approximately 0.1 ppm. The inactivity timer algorithm interacts with the timing manager function. The Update sync or PO Next output identifies for the timeout manager the MC pulse that matches the beginning of the PO or the sync Update following an activation. The Start of PO entry from the Timing Manager identifies for the inactivity timer algorithm the beginning of a PO following an activation. If the FTC changes the frame timing after a Sync Update, the indicated Start Time of PO is with respect to the updated timing. The inactivity timer algorithm compares the real-time clock frequency measurement and the inactivity timer programming. With respect to the real-time clock frequency measurement, FIG. 5 is a timing diagram of a RTC frequency estimation window, according to the present invention. To measure the frequency of the RTC with accuracy, a count of the number of master clock pulses 271 is performed for a prolonged period of time 272. The master clock has a frequency of 76.8 MHz, which is a chip frequency 20X. Since this watch has a phase lock for TCXO, its worst accuracy is 0.1 ppm. Since there is no correction of the RTC, the accuracy of the TCXO does not affect the accuracy of frequency measurement of RTC. As a result, the frequency measurement accuracy of RTC can be increased as required, by increasing the size of the frequency estimation window. For an accuracy of RTC frequency estimate of 0.1 ppm, a count of 10 million Master Clock (MC) 271 pulses should be performed. When the length of the frequency estimation window is selected in 4096 RTC pulses ("ticks" ") v includes 9,600,000 MC pulses for the nominal RTC frequency of 32,768 Hz and a master clock frequency of 76.8 MHz. The start and end of the frequency estimation window are both triggered by RTC pulses 271. The start of an RTC pulse 271 starts the MC pulse count. At the beginning of pulse number 4096 of RTC 271, the counting of the MC is stopped, and the counter value of MC is used for a frequency estimation. The frequency estimation window is extended for approximately 125 ms or 13 frames. In active connected mode this frequency estimate is not carried out, except just before entering the DRX cycles. In this case, frequency measurement occurs anywhere in the last 100 frames before entering the DRX cycles. During DRX cycles, the frequency measurement is carried out within each sync update period. Frequency processing and measurement should occur in the last 13 frames of sync update periods, so that the TCXO has the maximum possible time in which to install. The updated frequency estimate is used in the next location block. Regarding the programming of the timer and inactivity, Figure 6 is a timing diagram showing the programming of the inactivity timer. The inactive timer determines two periodic cases for each DRX cycle; the time of the next activation for the TCXO; and the time (specific MC pulse) of the next PO or the beginning of the next sync update block, whatever the next case. To locate these cases in the absence of a TCXO, there is a measurement and various procedures to apply to simple counting operations. In Figure 6 below, the time diagram for events is shown. TIC A: First Tic of RTC after a PO. TIC B = BRTC: the RTC tic where TCXO power increases BRTC specifies the number of RTC ticks from the beginning of a PO (calculated each sync update or DRX cycle length change). ICT C = CRTC: the RTC tick in the XRD period used to locate the next PO or the start of the Synchronization Update Block (calculated for each sync update) KRTC (= 4096): the period of the frequency estimation window in terms of the number of RTC ticks (constant) DRXP: this parameter indicates the distance from the current PO to the Next Case in terms of frames. It has different values according to the Next Case entry and the DRX cycle length, which are provided in Table 1. KMC: the number of MC pulses (20X) per DRX period (tabulated for all DRX cycle lengths) KRTC: the number of RTC pulses used during frequency estimation, which is set to 4096. MMc- "the measured number of MC pulses in the RTC frequency measurement window (measured for each synchronization update period.) AMC: the measured number of MC pulses from the beginning of the current PO to the Tic A (measured for each DRX cycle) BRTC: active TCXO time in terms of pulses of RTC, which is approximately equal to 5 msec (expressed as 164 RTC ticks), before the beginning of the sync Update Block or next PO. CMC: the calculated number of MC ticks from CRTC (Tic C) to the beginning of the sync update block or the next location block. The start of the CMC pulse is approximately the same time as the start of the first chip in the sync Update Block or the next Location Block. At the beginning of each location block, the time of the next activation is calculated. This is done in the following way: 1) the number of MC pulses, AMC, is measured from the PO to the next RTC pulse (TIC A); 2) the DRXP is found from Table 1; and 3) BRTC CRTC AND CMc are calculated using the formulas in the Equation. Figure 7 is a flow diagram 300 for TCXO shutdown procedures during DRX. The beginning of a location block (step 301) is followed by the AMc Measurement (step 302), followed by the calculation of BRTC, CRTC and CMc (step 303). These calculations are followed by a PICH reading (step 304), followed by a determination as to whether a location indicator (Pl) is positive (step 305). If the Pl is positive, the WTRU is located or there is a change in some configurations, as indicated by the BCCH. Therefore, if the Pl is positive, the WTRU will read the PCH channel to discover what the positive Pl refers to. If the Pl is positive, the PCH is read (step 311) and a determination is made as to whether the data read from the PCH indicates a BCCH modification or located (step 312). If the data read from the PCH indicates a BCCH modification or localized, as determined in step 312, the TCXO remains on, or the DRX mode ends (step 313). If the Pl is not positive, as determined in step 305, or the PCH does not indicate a 'BCCH modification or localized, as determined in step 312, a determination is made as to whether the current PO follows correctly to a sync update (step 321). If the current PO follows correctly to a sync update, the procedure waits until AFC and FTC converge (pass 322), and the time when AFC and FTC converge is determined whether the distance from the AFC / FTC convergence declaration to the beginning of the following case is greater than 1 frame (step 323). If the distance from the AFC / FTC convergence declaration to the beginning of the next case is greater than 1 frame, the TCXO is turned off and the DRX mode continues (weight 324). If the distance from the AFC / FTC convergence declaration to the beginning of the next case is not greater than 1 frame, as determined in step 323, the TCXO remains on but the DRX mode continues. If the current PO does not follow a sync update, as determined in step 321, neighboring search measurements are made until it is complete (step 341), and a determination is made as to whether the distance from the current PO to the beginning of the following sync update is less than 17 frames (step 342). If the distance from the current PO to the beginning of the next sync update is less than 17 frames, the TCXO is turned off and the DRX mode continues (step 324). If the distance from the current PO to the beginning of the next sync update is not less than 17 frames, the TCXO remains on but the DRX mode continues. In operation, the next case of the inactivity timer is to program the TCXO shutdown, which is represented in the flow diagram. As can be seen in the flow chart, there are three final cases of programming per DRX cycle: 1) the TCXO is closed, the WTRU remains in DRX and the inactivity timer algorithm is applied 2) 6-1 TCXO remains ON due to conditions shown in the flow diagram and the WTRU remains in DRX. The clock reference used is TCXO and the inactivity timer algorithm is not used; and 3) the TCXO remains ON and the WTRU must leave DRX. In this case, the WTRÜ has been located or BCCH modification information is present. Table 1: DRXp vs. Next case (*) The TCXO is already ON for this case, as explained above.

The final step of the. procedure is the activation for the Next Case. The activation procedure is as follows: 1) turn on the TCXO in time BRTC, the pulse of BRTC after the last PO; 2) Wait until the CRTC time; 3) carry out the counting of master clock pulses CMC starting from CRTc 4) on the master clock pulse CMC the time is approximately the same as the beginning of the Next Case, ie the first chip of the first time slot of the Case Following; and 5) repeat the procedure for each DRX cycle until the WTRU exits the DRX cycles. An advantage of the invention is that it implements a very simple procedure, which avoids a real clock calibration requirement. The accuracy of the timing can be controlled by changing the length of the measurement period or the reference clock frequency. The simplicity comes from the fact that, this procedure mode does not calibrate the low accuracy clock but only measures its frequency.

Claims (29)

1. Method of operation of a wireless transmission / reception unit (WTRU), the method is characterized in that it comprises: providing a reference oscillator for synchronized communications; provide a real-time clock (RTC); provide an active mode of operation and a mode of operation of low power; use the reference oscillator during the active mode and do not use the reference oscillator during the low power mode; use the RTC during low power mode; and during the low power mode, make a frequency adjustment for synchronization from the RTC, thus fulfilling predetermined synchronization criteria.

Method according to claim 13, wherein the low power mode includes a discontinuous reception (DRX)

3. Method according to claim 2, characterized in that: the reference oscillator functions as an active high power and high oscillator accuracy; the RTC works as an alternative oscillator in the DRX mode; and an inactivity timer algorithm implements the DRX timing and controls the active and low power modes of operation to achieve this, using the reference oscillator in the active mode and not using the reference oscillator during the low power mode.

4. Method according to claim 1, characterized in that it comprises, during the low power mode, determining whether the predetermined cases meet the predetermined synchronization criteria, and in the case that the synchronization criteria are not met, providing an adjustment of synchronization for the synchronization obtained from the RTC.

Method according to claim 1, characterized in that it comprises using a temperature controlled crystal oscillator (TCXO) as the reference oscillator.

Method according to claim 1, characterized in that it comprises: during the low power mode, determining whether the predetermined cases meet the predetermined synchronization criteria; and in the case that the synchronization criteria are not met, provide a synchronization adjustment for the synchronization obtained from the RTC.

Method according to claim 1, characterized in that it comprises: providing a transition from the low power mode to the active mode in response to a location occasion (PO); provide a transition from the low power mode in response to a synchronization event.

8. A wireless transmission / reception unit (WTRU) comprising: a reference oscillator that provides a frequency standard for synchronized communications; a real-time clock (RTC) that operates at a power significantly lower than the reference oscillator; a circuit to implement a RTC frequency standard based on the RTC; a controller to provide an active mode of operation and a low power mode of operation, chicken which the active mode uses the reference oscillator and the low power mode uses the RTC frequency standard; and a circuit for effecting a frequency adjustment for synchronization from the RTC, at least during the low power mode, thus fulfilling predetermined synchronization criteria.

9. WTRU according to claim 8, characterized in that: the low power mode includes a discontinuous reception (DRX); the reference oscillator functions as a high-power, high-accuracy oscillator; the RTC works as an alternative oscillator in the DRX mode; and the controller implements an idle timer algorithm to control the implementation of the DRX timing and control the active and low power modes of operation to achieve this using the reference oscillator in the active mode and not using the reference oscillator during the mode of low power.

10. WTRU according to claim 8, comprising a temperature-controlled crystal oscillator (TCXO) provided as the reference oscillator.

11. WTRU according to claim 8, characterized in that it comprises: the controller that provides a determination as to whether the predetermined cases meet the predetermined synchronization criteria during the low power mode; and in the event that IQS synchronization criteria are not met, the controller executes a command to effect a frequency adjustment for synchronization obtained from RTC

12. WTRU according to claim 11, characterized in that it comprises: the controller that provides a transition from low power mode to active mode in response to a location occasion (PO); and the controller that provides a transition from the low power mode in response to a synchronization event.

13. Frequency standard for use in electronic devices with active and inactive modes of operation, frequency standard comprising: a reference oscillator that provides a first oscillation accuracy; ? .n real-time clock (RTC); a circuit for deriving a reference oscillation signal from the RTC, where the RTC and the circuit for deriving the reference oscillation signal from the RTC operate at a power significantly lower than the reference oscillator; a circuit for effecting a frequency adjustment for synchronization from the RTC, thus fulfilling predetermined synchronization criteria in a second oscillation precision; and a controller to provide an active mode of operation and a low power mode of operation, whereby the active mode uses the reference oscillator and the low power mode uses the reference oscillation signal from the RTC and not the oscillator reference.

14. Frequency standard according to claim 13, characterized in that: the low power mode includes a discontinuous reception (DRX); the reference oscillator functions as a high-power, high-accuracy oscillator; the RTC works as an alternative oscillator in the DRX mode; and the controller uses an idle timer algorithm to implement the DRX timing and to control the active and low power modes of operation to achieve this using the reference oscillator in the active mode and not using the reference oscillator during the low mode power.

15. Frequency standard according to claim 13, characterized in that, during the low power mode, the controller determines whether the predetermined cases meet the predetermined synchronization criteria, and in the case that the synchronization criteria are not met , the controller executes a command to effect a frequency adjustment for the synchronization obtained from the RTC.

16. Frequency standard according to claim 13, characterized in that it comprises a temperature-controlled crystal oscillator (TCXO) provided as the reference oscillator.

17. The frequency standard according to claim 13, characterized in that it comprises: the controller that provides a transition from the low power mode to the active mode in response to a location occasion (PO); and the controller that provides a transition from the low power mode in response to a synchronization event.

18. Method of operation of a wireless transmission / reception unit (WTRU), the method characterized in that it comprises: establishing a discontinuous reception state (DRX) during which the WTRU operates in a discontinuous reception operation mode; set a reduced clock speed for the DRX mode using a reference oscillator; determining a timing of synchronization of received signals according to the reduced clock speed; determining, in accordance with the received signals, a state of location interval; in the case of at least one predetermined location interval state, discontinue the DRX state and initiate a standard operating state; and in the case of at least one other location interval state, continue with the DRX state.

19. Method according to claim 18, characterized in that it comprises establishing at least one synchronization state in response to the other location state.

20. Method according to claim 18, characterized in that it further comprises: using a reference oscillator for synchronized communications in the standard operating state; and use a real-time clock (RTC) for synchronized communications in the DRX mode.

21. Method according to claim 18, characterized in that it further comprises: providing an active mode of operation as the standard operating state and a low power mode of operation such as the DRX mode; use the reference oscillator during the active mode; use a real-time clock (RTC) for synchronized communications in DRX mode; and during the low power mode, make a frequency adjustment for synchronization from the RTC, thus fulfilling predetermined synchronization criteria.

22. Method according to claim 18, characterized in that it further comprises: receiving a state of location; determine a reception timing of the location state; and in the event that reception of the location state occurs within a period of time prior to a synchronization update, preserve a standard operating status until the next synchronization update. '• »

23. Method according to claim 22 '", characterized in that it further comprises: determining a state of FTC, determining a state of convergence of FTC and automatic frequency control, and if the state of convergence of FTC and automatic frequency control exceeds predetermined limits 24. Consist of a standard operating state until the next synchronization is updated 24. Method according to claim 18, characterized in that: the reference oscillator functions as a high-power, high-accuracy oscillator, the RTC functions as an alternative oscillator in the DRX mode, and an idle timer algorithm implements the DRX timing and controls the active and low power modes of operation to achieve this using the reference oscillator during the active mode and not using the reference oscillator during the low power mode 25. A semiconductor integrated circuit in use in a wireless device The integrated circuit is characterized in that it comprises: a reference oscillator that provides a frequency standard for synchronized communications; a real-time clock (RTC) that operates at a power significantly lower than the reference oscillator; a circuit to implement a RTC frequency standard based on the RTC; a controller for providing an active mode of operation and a low power mode of operation, by means of which the active mode uses the reference oscillator and the low power mode uses the frequency standard of the RTC; and a circuit for effecting a frequency adjustment for synchronization from the RTC, at least during the low power mode, thus fulfilling predetermined synchronization criteria. Integrated circuit according to claim 25, characterized in that: the low power mode includes a discontinuous reception (DRX), the reference oscillator functions as a high power and high accuracy oscillator; the RTC works as an alternative oscillator in the DRX mode; and the controller implements an idle timer algorithm to control the implementation of the DRX timing and control the active and low power modes of operation to achieve this using the reference oscillator during the active mode and not using the reference oscillator during the mode of low power. 27. Integrated circuit according to claim 25, characterized in that it comprises a temperature-controlled crystal oscillator (TCXO) provided as the reference oscillator. Integrated circuit according to claim 25, characterized in that it comprises: the controller that provides a determination as to whether the predetermined cases meet the predetermined synchronization criteria during the low power mode and in the case that the synchronization criteria, the controller that executes a command to effect a frequency adjustment for the synchronization obtained from the RTC. Integrated circuit according to claim 11, characterized in that it comprises: the controller that provides a transition from the low power mode to the active mode in response to a location occasion (PO); and the controller that provides a transition from the low power mode in response to a synchronization event.