|Title of Invention||
METHOD FOR OPTIMIZING GAP SCHEDULING BETWEEN USER EQUIPMENT AND A NETWORK
|Abstract||ABSTRACT The proposed method optimizes the gap switching between the user equipment and the network. The said gaps are part of the larger measurement gap pattern established by the network for the user equipments which need to perform gap-assisted measurement in a wireless cellular system to measure neighboring cells on different frequency/ layer or radio access technology. In this method gap scheduling (switching gaps on or off) depends on pre-defined CQI thresholds which are configured by the network and which shall enable the user equipment to use and schedule the gaps and therefore the gap pattern (established by the network beforehand) on its own without requiring any explicit signaling from the network. By using this method, the explicit signaling for gap scheduling is avoided thereby reducing the radio load of the network. The method uses CQI measurement & reports (channel quality indicator) to estimate the radio quality which is a more reliable measure to depict the BLER performance.|
|Full Text||FIELD OF THE INVENTION
The present invention, in general, relates to the field of mobile communications especially where the measurement gaps are used by the user equipment to perform the inter frequency/ Layer/ RAT measurements. This invention pertains to the layer 1 and layer 3 of the protocol stack of the said systems. More particularly, the present invention relates to method of measurement gap scheduling.
DESCRIPTION OF THE RELATED ART
A measurement gap pattern is an arrangement of scheduling gaps provided by the network for the user equipment which are othenwise not capable to simultaneously measure a neighboring frequency, so that the latter can be relieved of the current frequency (temporarily) and can find time out to measure the neighboring frequency/ layer or RATs using the gaps in the gap pattern. The gap pattern is supposedly established by the network using explicit signaling; once established the UE may keep using the 'gaps' as long as desirable.
At present a Gap pattern is to be initiated/ started by an explicit command from the network and it is released/ stopped by the network using explicit signaling. Gaps (gap pattern) are only provided when the present cell/ frequency/ layer/ RAT quality goes below a certain threshold and thereby the UE connection
needs to be moved to some other frequency/ layer/ RAT for quality/ coverage reasons. If the present cell/ frequency/ layer/ RAT quality becomes better than a pre-defined threshold then the inter measurements are no more necessary and the gap requirement ceases. Network may need to know about this situation (that no more gaps are required) for its scheduling freedom. There are two potential issues with this:
1. The present cell quality may be based on CPICH Eclo or CPICH RSCP, which may not be the best indicator of channel quality.
2. The explicit signaling to switch on and off the gaps should be avoided. So that it should be possible for a UE to autonomously control the gap scheduling based on the present channel conditions.
United States Patent 20070097914: MOBILE DEVICE-INITIATED MEASUREMENT GAP REQUEST discusses initiating the measurement gap using the CQI reports from the user equipment BUT does not talk about "gap switching (on-off)" or releasing the measurement gap based on the CQI reports from UE (CQI reports are below a certain threshold).
Another Patents US 6,810,019 B2: Reducing Interference In Inter-Frequency Measurement discusses more towards explanation of a gap pattern.
SUMMARY OF THE INVENTION
The present invention relates to the field of mobile communication. More specifically, the present invention provides a method to optimize the gap scheduling between a User Equipment (UE) and a network. The network configures Channel Quality Indicator (CQI) thresholds to indicate the start and stop of cell measurements. When the UE detects that CQI has dropped below a first threshold value, it reports the first threshold value to the network. The network establishes a gap pattern for cell measurements so that the UE can search for a better cell. The UE starts cell measurements and reports the CQI threshold to the network. If the CQI threshold value goes above a second threshold, the UE stops measurements. Further, the UE stops using the gap pattern as it has found a cell with better CQI. The second threshold is reported to the network. After a particular time interval, if the CQI threshold again goes below the first threshold, the UE indicates the CQI threshold to the network. The UE starts using the previous established gap pattern again after a predefined time interval for cell measurements. Therefore, once the gap pattern is established by the network, the UE is able to use the gap pattern on its own without requiring any explicit signalling from the network.
Accordingly the invention explains a method of measurement gap scheduling between a User Equipment (UE) and a network where the network configures Channel Quality Indicator (CQI) thresholds to indicate the start and stop of cell measurements.
When the UE detects that CQI has dropped below a first threshold value, it reports the first threshold value to the network and the network establishes a gap pattern for cell measurements so that the UE can search for a better cell. The UE starts cell measurements and reports the CQI threshold to the network and if the CQI threshold value goes above a second threshold, the UE stops measurements. The UE stops using the gap pattern as it has found a cell with better CQI and a second threshold is reported to the network. After a particular time interval, if the CQI threshold again goes below the first threshold, the UE indicates the CQI threshold to the network and the UE starts using the previous established gap pattern again after a predefined time interval for cell measurements. Once the gap pattern is established by the network, the UE use the gap pattern on its own without requiring any explicit signalling from the network.
These and other objects, features and advantages of the present invention will become more apparent from the ensuing detailed description of the invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 depicts "Traditional Approach" to handle Gap Scheduling Figure 2 depicts proposed way to handle Gap Scheduling
DETAILED DESCRIPTION OF THE INVENTION
The preferred ennbodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.
Referring to Figure 1, it depicts the traditional way to perform measurement and gap scheduling. After the Intra measurements (Eclo or RSCP of the current frequency cells) has been setup by the network (Step1), the UE keeps performing the Intra measurements (Step2). Intra quality here means the RSCP or Eclo of the pilot channel. When the intra quality goes bad (step3), the same is reported to the network (Step3). Network then understands that the present frequency is not good enough for the connection and therefore it has to prepare the UE for handover to another frequency/ layer/ RAT. It sends the Measurement control message for configuring the measurements in the UE. The Gap pattern can be communicated to the UE in the same message or may be communicated
separately (Step4). UE now performs both intra and inter quality measurements (Step5). When the intra quality gets better (above a certain threshold) the UE indicates this in a measurement report message to the network (Step6). Network upon receiving the message releases the Gap pattern and measurement (Step7). Next time when the Inter measurement is required (the present cell/ frequency/ layer quality goes below a certain threshold), and then the entire procedure will be repeated.
In Figure 2 on the other hand it explain the proposed method. Steps 1 and 2 work as above except that in step 2 UE performs the CQI measurement based on DL channel sounding/ reference signals. In step 3 the measurement report indicates the CQI value below a certain threshold. In step 4 the Inter measurements are configured and probably the Gap pattern is also established by the network (the Gap pattern can also be signaled in a separate message). Once the Inter measurements have been configured, the user equipment keeps performing the Inter measurements and CQI reporting for the current cell (Step 5). In step 6, the present cell gets better and the CQI values go above a certain threshold; UE stops the inter measurement and therefore stops using the gap. CQI report is sent to the network (Step 7) indicating the termination of UE measurement and gap usage by the user equipment (Step 8).
The Gap pattern establishment (and probably the Inter measurement configuration) act as one time setup by the network and next time if the CQI report of the present cells 'again' goes below a certain threshold then the
complete signaling may not be repeated again; UE may indicate the bad CQI to network and start using the Gap pattern (last established) after a predefined time interval. Network may however change either the Gap pattern or measurement configuration using an explicit signaling, if required.
A traditional wireless system facilitates preparation of inter-radio access technology (inter-RAT) and/or inter-frequency handover or inter-layer handover with respect to a mobile device (user equipment) using explicit signaling. User equipment can indicate to a network servicing the user equipment that the user equipment desires to perform measurements with respect to a different frequency and/or different technology. This typically happens when the present cell/ frequency/ RAT quality deteriorates. Data on the downlink channel can then be scheduled to ensure that data intended for the user equipment is not lost while the user equipment is performing the measurements. Inter Measurements are classified as gap assisted or non gap assisted, depending on whether the UE needs transmission/reception gaps to perform the relevant measurements.
In traditional wireless system, the parameters often used for this purpose (to decide about the present quality) are typical quality parameters like RSCP and Eclo. RSCP and Eclo fluctuations are traditional methods of detecting a poor signal condition where common pilot is used to estimate channel quality; their values don't directly depict the actual impact on BLER performance and synchronization status.
In traditional wireless system, signaling as described in the figure 1 is explicit i.e. to establish/ release a measurement configuration or to establish/ release a gap pattern, explicit messages are used. These wireless systems could use either the RRC or MAC signaling.
This invention describe a method wherein the use of explicit signaling is obviated for Gap scheduling. It envisages a model in which the Gap pattern is initially assigned to the UE at the start of each Gap assisted measurement (when the network comes to know about the bad quality of present frequency). For better reliability and performance it has been relied upon CQI reports rather than quality measurements like RSCP or Eclo. So here is has been describing the method of Measurement Gap scheduling, which is implicit in nature and based on CQI reports from the user equipment.
As described in figure 2, the network pre-configures two thresholds with the user equipment either in the measurement control message (to establish the Intra measurements) or in a separate message. One of these thresholds (thresh_A) indicates that the present cell/ frequency CQI is below a certain threshold and other threshold (thresh_B) indicates that the present cell/ frequency CQI is above a certain threshold. Thresh_B will naturally come only after the thresh_A has occurred.
The Gap pattern is established for the first time by the network when the thresh_A occurs (event reported by the user equipment based on the said
threshold established by the said measurement control message) and UE reports this value to the network. Network may select the right Gap pattern for the UE based on various factors like UE capability, network load and scheduling optimizations etc. Once the gap pattern is established the user equipment and the network abide by the resulting scheduling due to the presence of said gaps. Henceforth the user equipment may keep reporting the inter measurements to the network. The network shall command the user equipment when a suitable cell is found from the measurement reports received from the user equipment. Such a suitable cell must have passed the handover selection criteria. In absence of availability of such suitable cells the user equipment keeps measuring until a suitable cell is found or the quality of the present cell/ frequency or RAT goes above a certain threshold thresh_B (as described above). When the quality of the present cell/ frequency or RAT goes above thresh_B, the user equipment shall infer that the present cell/ frequency/ RAT quality (CQI) is sufficiently fine to carry on with the existing call. In such a scenario the user equipment shall stop using the gaps provided by the said established gap pattern and cease to perform the inter measurements. The user equipment shall however send the CQI report to the network. Network upon the receipt of CQI report from the user equipment shall understand that the present cell/ frequency quality has gone above a certain threshold and therefore no more gaps are required by the said user equipment. The network henceforth can use the said gaps for further scheduling giving it more scheduling freedom.
The gap usage may again implicitly start if the thresh_A occurs and after the
user equipment has sent the corresponding CQI report to the network. The network reserves the right to modify/ release the Gap pattern at any point of time.
The main inventive concept of the invention is as follows:-
Gap scheduling (switching gaps on or off) depends on pre-defined CQI thresholds which are configured by the network and which shall enable the user equipment to use the gap pattern (established by the network beforehand) on its own without requiring any explicit signaling from the network.
As compared to traditional wireless system this will have the following advantages:
1. The quality estimate is based on more reliable parameter CQI which should be more realistic in depicting the BLER performance.
2. The gap scheduling signaling will not require explicit RRC or MAC signaling thereby reducing the radio load.
It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the
applications include but not limited to a microchip, microprocessor, handheld communication device, computer, rendering device or a multi function device.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart there from.
3L0SSARY OF TERMS AND DEFINITIONS THEREOF
3G: Third Generation mobile communication
RAT: Radio Access Technology
LTE: Long Term Evolution
eNB: Enhanced NodeB
UE: User Equipment
UMTS: Universal Mobile Telecommunications system
RNC: Radio Network Controller
RRC: Radio Resource Control
MAC: Medium Access Control
RLC: Radio Link Control
CQI: Channel quality indicator
Intra measurements: Measurements of the neighboring/ current/ serving cells on the current frequency
Inter Measurements: Measurements on the neighboring frequency/ radio access technology.
RSCP: Received Signal Code Power
Eclo: The ratio of received pilot energy, Ec, to total received energy or the total power spectral density, lo
BLER: Block Error Rate
1. A method of measurement gap scheduling between a User Equipment (UE) and a network where the network configures Channel Quality Indicator (CQI) thresholds to indicate the start and stop of cell measurements.
2. A method as claimed in claim 1 wherein, when the UE detects that CQI has dropped below a first threshold value, it reports the first threshold value to the network and the network establishes a gap pattern for cell measurements so that the UE can search for a better cell.
3. A method as claimed in claim 1 wherein, the UE starts cell measurements and reports the CQI threshold to the network and if the CQI threshold value goes above a second threshold, the UE stops measurements.
4. A method as claimed in claim 1 wherein, further, the UE stops using the gap pattern as it has found a cell with better CQI and a second threshold is reported to the network.
5. A method as claimed in claim 1 wherein after a particular time interval, if the CQI threshold again goes below the first threshold, the UE indicates the CQI threshold to the network and the UE starts using the previous
established gap pattern again after a predefined time interval for cell measurements.
6. A method as claimed in claim 1 wherein once the gap pattern is
established by the network, the UE use the gap pattern on its own without
requiring any explicit signalling from the network.
7. A method of measurement gap scheduling substantially described
particularly with reference to the accompanying drawings.
|Indian Patent Application Number||2347/CHE/2007|
|PG Journal Number||38/2013|
|Date of Filing||16-Oct-2007|
|Name of Patentee||SAMSUNG INDIA SOFTWARE OPERATIONS PRIVATE LIMITED|
|Applicant Address||BAGMANE LAKEVIEW BLOCK 'B' NO 66/1BAGMANE TECH PARK C.V RAMAN NAGAR,BYRASANDRA.BANGALORE 560093|
|PCT International Classification Number||H 04 Q 07/00|
|PCT International Application Number||N/A|
|PCT International Filing date|