DE102012015943A1 - User device, has hardware controller coupled to radio frequency front end, where synchronous signal is extracted from storage device by hardware controller to execute initial unit searching process - Google Patents

Abstract

The device has a hardware controller coupled to a radio frequency front end. The radio frequency front end is utilized for creating resynchronization data. The resynchronization data is transferred to a storage device i.e. external storage device. An initial unit searching module is coupled to the hardware controller. A synchronous signal is extracted from the storage device by the hardware controller to execute an initial unit searching process. The hardware controller is coupled to the storage device through an external storage interface. Independent claims are also included for the following: (1) a method for searching an initial unit in a user device (2) a chip.

Description

BACKGROUND OF THE INVENTION

1. Technical area

The invention generally relates to mobile communications, and more particularly to the initial cell search procedure in mobile communications.

2. State of the art

Prior to setting up a network connection, a UE (user equipment, such as a (cell-based) mobile phone) in a mobile communications network must first perform an initial cell search (ICS) procedure to determine in which should be dwelled on a variety of nearby cells and how to communicate with the cell.

In general, the UE has a crystal oscillator serving as a local oscillator, hereinafter LO, for generating an LO signal. The LO signal is used to down-convert the high-frequency signals, hereinafter RF signals, which the UE receives to the baseband domain. Since the crystal oscillator is sometimes not exact, it may be necessary for the UE to respond to the problem of a frequency offset caused by the non-exact LO signal during the ICS procedure. However, this may extend the acquisition time used to complete the ICS procedure.

In addition to the frequency offset problem associated with the crystal oscillator, conventional techniques for the ICS procedure may present other problems, such as: B. a long detection time and excessive energy consumption.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the aforementioned problems. The solution of this object is achieved by a user device having the features according to claim 1, a chip having the features according to claim 6, an initial cell search module having the features according to claim 10 and a method having the features according to claim 11. The subclaims disclose preferred developments of the present invention , In addition, the invention provides some embodiments for solving the aforementioned problems.

An embodiment of the invention provides a UE. The UE has an RF input unit, in the following RF FE, a hardware control unit, hereafter HW control unit, and an ICS module. The RF FE is arranged to recover synchronization data based on the RF signals received from the UE. The hardware controller is arranged to store the synchronization data which restores the RF FE into a memory of the UE and to fetch the synchronization data from the memory. The ICS module is arranged to use the synchronization data which the hardware controller retrieves from memory for undertaking an ICS attempt.

Another embodiment of the invention provides a chip for installation in a UE. The chip has a HW control unit and an ICS module. The HW control unit is set up to store synchronization data, which the UE recovers, via an interface for an external memory, in the following EMI, of the chip into a memory of the UE and then to fetch the synchronization data from the memory by the EMI. The ICS module is set up to use the synchronization data fetched from memory by the HW controller to make an ICS attempt.

Another embodiment of the invention provides an ICS method performed by a UE. According to the method, synchronization data is first recovered based on RF signals received from the UE. Subsequently, the synchronization data are stored in a memory of the UE. The synchronization data is then retrieved from memory and used to undertake an ICS attempt.

Other features of the present invention will become apparent from the accompanying drawings and from the following detailed description.

Brief description of the drawings

The invention will be more fully understood from the ensuing detailed description and the accompanying drawings with further details, features, and advantages, in which like reference numerals denote like elements.

1 FIG. 12 is a schematic diagram of an exemplary synchronization frame used in a third generation (3G) mobile communication network. FIG.

2 shows a simplified block diagram of a UE according to an embodiment of the invention.

three Figure 12 shows a simplified flowchart of one by the UE 2 performed procedure.

Detailed description

In a mobile communication network, each cell may broadcast synchronization frames one after another to support nearby UEs in performing the ICS procedure. From the perspective of the UE, the synchronization frames broadcast by the nearby cells may overlap each other in the time domain. In the ICS procedure, the UE may use the overlapping synchronization frames to determine in which cell to stay and how to communicate with the cell.

1 FIG. 12 shows a schematic diagram of an exemplary synchronization frame used in a 3G mobile communication network. FIG. As this diagram shows, the synchronization frame uses three synchronization channels, which contain a primary synchronization channel, hereinafter called PSCH, a secondary synchronization channel, hereinafter SSCH, and a common pilot channel, hereinafter CPICH. The synchronization frame is divided into 15 time slots. In the PSCH, a sequence is broadcast at the beginning of each timeslot. The 15 PSCH sequences in the synchronization frame are all the same; they allow a UE to perform slot synchronization, which is defined in stage 1 of the ICS procedure. In SSCH, a sequence is broadcast at the beginning of each timeslot. The 15 SSCH sequences in the synchronization frame are different; they allow the UE to perform frame synchronization and code group identification defined as level 2 of the ICS procedure. By dividing each of the 15 timeslots into 10 symbols, the CPICH carries the common downlink pilot symbols scrambled by a specific scrambling code. The common downlink pilot symbols enable the UE to perform scrambling code identification, which is defined as level 3 of the ICS procedure. The 4G mobile communication standard ICS procedure (ie 4G LTE) also has three stages similar to the above three stages.

2 shows a simplified block diagram of a UE according to an embodiment of the invention. This diagram shows only the functional blocks that are essential to the invention; other functional blocks are omitted therein for the sake of simplicity. The UE 200 can be compatible with 3G and / or 4G mobile communication standards.

In this embodiment, the UE contains 200 an RF FE 210 , a HW control unit 220 , an ICS module 230 and a memory 240 , The memory 240 is not an internal memory of a chip 215 that the HW control unit 220 and the ICS module 230 but is outside the chip 215 arranged and through an interface for an external memory 225 , hereinafter EMI 225 , the chip 215 with the chip 215 connected. The storage interface 225 is an external one, as it is not inside the chip 215 is arranged. The chip 215 can through the HW control unit 220 and the EMI 225 on through the store 240 access the space provided. Even though 2 this is different, the RF FE 210 also a part of the chip 215 be. The RF FE 210 is intended to RF signals, which is an antenna of the UE 200 receives down to the baseband area. To perform the downconversion of the frequency, the RF FE 210 Components include such. As a filter, a small signal amplifier or low noise amplifier 225 , hereinafter LNA, a local oscillator (LO) and a down conversion mixer.

20 shows a simplified flowchart of one by the UE 200 performed procedure. The figure shows only the essential steps for the invention; other steps are omitted for the sake of simplicity. First, the UE 200 in step 310 Restore sync data and put it in memory 240 to enable subsequent offline ICS. More specifically, the RF FE 210 the synchronization data is restored to the baseband domain by downconverting the RF signals which the antenna receives on the synchronization channels. The HW control unit 220 sets the synchronization data, which it receives from the RF FE 210 receives, into memory 240 ,

The synchronization data may include information within synchronization frames which simultaneously through multiple cells near the UE 200 be broadcast. For example, if the UE 200 a 3G UE, each of the synchronization frames is the one in 1 have shown structure. step 310 may take long enough for the UE to do 200 can detect the synchronization data with sufficient quality.

In step 310 can the HW controller 220 the synchronization data at the same time the ICS module 230 for some real-time ICS experiments. However, because step 310 It can only take a short time, it is possible that the ICS module 230 in step 310 can not complete a successful ICS trial. After step 310 can the UE 200 the RF FE 210 switch off to reduce energy consumption.

An ICS experiment is the attempt of an ICS process involving the ICS module 230 performs. For example, in the 3G standards, the ICS trial includes the aforementioned levels 1, 2, and 3. If the attempt is a serial attempt, only one of the three levels is currently allowed to work. If, on the other hand, the attempt is a pipeline attempt, the three stages can be carried out at the same time. Generally speaking, serial attempts can reduce energy consumption but mean a longer search time. In contrast, pipeline attempts can shorten the search time but mean higher energy consumption.

In step 320 determines the UE 200 whether the ICS module 230 then make an ICS attempt. If the answer is yes, the UE starts 200 with step 330 ; otherwise the UE jumps 200 to step 340 , For example, the UE 200 then make an ICS attempt if it is unable to finish the ICS procedure early or if it has not yet completed all attempts. If the ICS module 230 no real-time ICS attempt or real-time ICS attempts in step 310 performs the UE 200 step 320 skip and step 330 directly after leaving the step 310 kick off.

In step 330 uses the UE 200 from the store 240 fetched synchronization data to perform an ICS attempt offline. More precisely, the HW control unit fetches 220 the synchronization data from the memory 240 and sets the synchronization data to the ICS module 230 to disposal. The ICS module 230 uses the synchronization data to take the ICS attempt offline. The attempt is an off-line attempt, since the synchronization data is not real-time data, that is to say, there are no data broadcast concurrently by nearby cells, but less current data previously broadcast by nearby cells. The ICS module 230 can in step 330 make the ICS attempt either as a serial attempt or a pipeline attempt.

As in three shown, set the steps 320 and 330 an iterative loop which can be repeated several times until no further ICS experiments have subsequently been performed. As a result, the ICS module 230 the same part of synchronization data (which from memory 240 repeatedly) to perform multiple ICS experiments.

step 330 has for the UE 200 several advantages. For example, the RF FE 210 in step 330 be turned off, which is the total energy consumption of the UE 200 reduces and the battery charge is gentle. Further, for example, the offline ICS attempt may take less time than a real-time ICS attempt. More specifically, the duration of a real-time ICS trial may be equal to or longer than the duration of a synchronization frame. In contrast, the duration of an offline ICS attempt may be shorter than the duration of a synchronization frame, as the UE 200 Do not wait for the antenna to receive the sync frame and the RF FE 210 downconverts the sync frame. Therefore, the UE 200 linger for a shorter acquisition time in the ICS procedure.

It is likely that the UE 200 not much storage space 240 during the ICS procedure for reasons other than the ICS. In other words, the memory can 240 provide a lot of bandwidth for the ICS procedure. As a result, the UE 200 enough bandwidth for the memory 240 have to reserve this for the ICS procedure. In other words, in the steps 310 and 330 enough memory bandwidth for the HW controller 220 stand by to get the synchronization data into memory 240 store and then get the synchronization data from this. This use of memory 240 will most likely not use up all the available bandwidth. In addition, the UE 200 because of the memory 240 with high probability for other purposes than the ICS a required component of the UE 200 is the memory 240 for the ICS procedure without additional hardware costs or with low additional hardware costs.

The 10 of the RF FE 210 may comprise a crystal oscillator for generating an LO signal which is for down-converting the UE 200 received RF signals is used in the baseband area. Since the crystal oscillator may not be exact, the synchronization data may have an inherent baseband frequency offset and / or a timing drift. Therefore, the ICS module 230 before making the ICS attempt in step 330 undertake a digital baseband frequency shift with the synchronization data and / or perform digital time compensation with the synchronization data. Since these operations are performed digitally and on the basis of already stored synchronization data, they will not unduly delay the ICS procedure.

In step 340 determines the UE 200 whether it can stop the ICS procedure. If the answer is "No", the UE returns 200 to step 310 back to restart the ICS procedure; otherwise the UE goes 200 to step 350 , For example, the UE 200 the step 350 begin when the UE 200 has already received a best possible compensated frequency range (bin) or a bin with the best characteristic number or measure, and the quality of the bin with the best characteristic or measure number is better than a predefined threshold value.

In step 350 terminates the UE 200 the ICS procedure and lingers in a selected cell. More specifically, multiple operations may be required by the UE 200 after a successful ICS attempt and before actually lingering in a selected cell. 3G and 4G networks may require different sets of work steps, which can be done in step 350 must be performed.

In summary, several embodiments of the invention are provided. The UE has a radio frequency input unit, in the following RF FE, a hardware control unit, in the following HW control unit, and an initial cell search module, in the following ICS module. The RF FE is arranged to restore synchronization data based on RF signals received by the UE. The HW control unit is set up to store the synchronization data restored by the RF FE into a memory of the UE and subsequently to fetch the synchronization data from the memory. The ICS is arranged to use the synchronization data fetched from memory by the HW controller to make an ICS attempt. In this case, the embodiments described above enable the UE 200 to require a shorter acquisition time and to require less power for the ICS procedure. Furthermore, the embodiments allow the UE 200 to easily cope with the frequency offset and timing drift problems in the digital domain without the detection time or power requirements of the UE 200 to increase excessively. In addition, the embodiments may be implemented without or with minimal additional hardware costs.

In the foregoing detailed description, the invention has been described with reference to specific exemplary embodiments. It will be understood that these may be variously modified without departing from the spirit and scope of the invention as defined in the appended claims. The detailed description and drawings are therefore to be considered as illustrative and not restrictive.

Claims (13)

User device ( 200 ), hereinafter referred to as UE, comprising a radio frequency input unit ( 210 ), hereinafter referred to as RF FE, for restoring synchronization data based on RF signals received from the UE, characterized in that the UE ( 200 ) further comprises: - a hardware, hereinafter referred to as HW, control unit ( 220 ), which with the RF FE ( 210 ), which is set up, the synchronization data, which restores the RF FE, in a memory ( 240 ) of the UE ( 200 ) and then the synchronization data from the memory ( 240 ) pick up; and an initial cell search module ( 230 ), hereinafter referred to as ICS module, which with the HW control unit ( 220 ), and which is set up, the synchronization data which the HW control unit ( 220 ) from the memory ( 240 ) to use to make an ICS trial. UE according to claim 1, characterized in that the ICS module ( 230 ) is further set up by the HW control unit ( 220 ) from the memory ( 240 ) to repeatedly use synchronization data to make a variety of ICS attempts. UE according to claim 1 or 2, characterized in that the ICS module ( 230 ) is further configured to digitally shift a baseband frequency of the synchronization data before making the ICS attempt. UE according to one of the preceding claims, characterized in that the ICS module ( 230 ) is further configured to digitally compensate for timing drift of the synchronization data before attempting the ICS. UE according to one of the preceding claims, characterized in that an interface ( 225 ) for an external memory, hereinafter referred to as EMI, the hardware controller and the memory ( 240 ) connects to each other. Chip ( 215 ) for installation in a user equipment, hereinafter referred to as UE, comprising: - a hardware, hereinafter referred to as HW, control device which is set up, synchronization data recovered by the UE via an interface ( 225 ) for an external memory, hereinafter referred to as EMI, of the chip ( 215 ) into a memory ( 240 ) of the UE and then the synchronization data by the EMI from the memory ( 240 ) pick up; and an initial cell search module ( 230 ), hereinafter referred to as ICS module, which with the HW control unit ( 220 ), and is set up by the HW control unit ( 220 ) from the memory ( 240 ) used synchronization data to make an ICS attempt. Chip ( 215 ) according to claim 6, characterized in that the ICS module ( 230 ) is further set up by the HW control unit ( 220 ) from the memory ( 240 ) to repeatedly use synchronization data to make a variety of ICS attempts. Chip ( 215 ) according to one of claims 6 or 7, characterized in that the ICS module ( 230 ) is further configured to digitally shift a baseband frequency of the synchronization data before making the ICS attempt. Chip ( 215 ) according to one of claims 6 to 8, characterized in that the ICS module ( 230 ) is further configured to digitally compensate for timing drift of the synchronization data before attempting the ICS. Initial cell search method, hereinafter referred to as ICS method, which is provided by a user device ( 200 ), hereinafter referred to as UE, comprising a step of recovering synchronization data based on high-frequency signals, hereinafter referred to as RF signals, which the UE receives, characterized in that the method further comprises: storing the restored synchronization data in a memory ( 240 ) of the UE; and - retrieving the synchronization data from the memory ( 240 ) and using the fetched synchronization data to make an ICS attempt. The method of claim 10, characterized in that the method further comprises: repeating the retrieved synchronization data to make a plurality of ICS attempts. A method according to any one of claims 10 or 11, characterized in that the method further comprises: - digitally shifting a baseband frequency of the synchronization data before a company of the ICS attempt. A method according to any of claims 10, 11 or 12, characterized in that the method further comprises: digitally compensating a timing drift of the synchronization data before a company of the ICS attempt.

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