Title of Invention

METHOD FOR SUB-FRAME ID AND FRAME BOUNDARY DETECTION IN LONG TERM EVOLUTION (LTE) SYSTEMS

Abstract

The invention relates to communication protocols and more particularly to communication protocols in Line Terminal Equipment (L TE). The different detection protocols available for radio fram..e timing detection are: Synchronization Channel (SCH) based detection; Broadest Channel (BCH) based detection, and Reference signal-based detection. The present invention provides a unique way of identifying the Frame boundaries in multiple identical/ non identical SCH's in different sub-frames via the use of a new method called "sub frame position difference method", The method implements the use of the differences between the different sub frames carried by the SCH. The sub frame identity and hence the frame boundary can be identified by calculating the difference between the positions (based on time or number of slots/ sub-frames or any data packets) of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other.

Full Text

FIELD OF INVENTION The present invention in general relates to the field of Communication Protocol in LTE systems - Layerl (Physical Layer). More particular, this invention relates to a system and method for sub-frame Id and Frame boundary detection in LTE. DESCRIPTION OF RELATED ART In the current specification document 3GPP TR 25.814 v7.0.0 (2006-06) there are three different options for radio frame timing detection: SCH based detection, BCH based detection, and reference signal-based detection. SCH based detection The SCH based detection is applicable to both the hierarchical SCH and non- hierarchical SCH. With SCH based detection, the radio frame timing can be estimated by detecting the cell-specific SCH sequence in the frequency domain employing the SCH symbol timing detected in the previous step. When the primary SCH and secondary SCH are used in the hierarchical SCH, coherent detection of the cell-specific secondary SCH can be performed using the primary SCH as a reference signal. BCH based detection The BCH based detection is applicable to both the hierarchical SCH and non- hierarchical SCH. For BCH-based frame-timing detection, the frame-timing is detected by decoding the BCH. This may include hypothesis testing if the BCH is transmitted less frequently than the SCH. This method requires BCH reception both for the initial cell search and neighboring cell search. Reference signal based detection The reference signal based detection is primarily considered for the hierarchical SCH. The frame timing information is detected by the reference signal waveform (modulation pattern). In this case, the repetition interval of the reference signal waveform should be equal to the radio frame period, 10 msec SCH based detection: Necessity of detecting the cell-specific SCH sequence in the frequency domain employing the SCH symbol timing detected in the previous step. Lot of (512 or more) cell-specific SCH sequences need to exist and also the UE will need to detect them by using processes like correlation which could be time consuming, also the UE needs to store these cell-specific sequences. BCH based detection: This mandates the BCH reception for initial cell search which is not desirable. However, the hypothesis testing if the BCH is transmitted less frequently than the SCH is still not done and may defeat the purpose. Reference signal based detection: This method has additional dependency on reference signal waveform (modulation pattern) detection. Only upon reading of the reference signal contents can the timing be arrived upon. Also, it is only scheduled to be transmitted once in a 10 msec so it imposes an additional delay in the frame boundary detection. The cell search procedure should be independent of any such signal waveform detection. US patent publication bearing no. US20030169702A1 describes a method of cell searching in a Wideband-CDMA (W-CMDA) mobile communication. According to the patent publication, an "index counter" is used to continuously calculate the timing offset or offset between frame boundaries. The index counter comprises of a "slot counter" and a "lower counter" which are used respectively for, counting the slots, and the chips corresponding to a length of a predetermined number of slots. Further, the patent publications specifies, that once the position of each asynchronous cell is determined by the slot counter it is possible to calculate the offset between them wherein, the offset is defined as the difference between asynchronous frame boundaries. Moreover, the patent publication describes that, using a similar process the lower counter may be able to calculate the offset between the slots corresponding to each frame. Also, it has been mentioned in the patent publication that such an algorithm is more time efficient for cell search. Another US patent publication bearing no. US6574267B1 describes an improvement to code-division-multiple-access (CDMA) system employing spread- spectrum modulation between a Base Station (BS) and a Remote Station (RS). The process starts with one RS receiving a broadcast common - synchronization channel data, and after determining frame timing from the frame-timing signal, it is transmitted from a first RS-spread-spectrum transmitter as an access - burst signal. According to the patent publication, the BS notifies the RS about the correct receiving of the data packets. As an example, it has been specified in the patent publication that the packet could be identified as consisting of a number of frames, and sub-frames to the frames. The frames and sub-frames are identified by specific numbers. Further, the patent publication describes that the correctness of the receiving data packets could be achieved by identifying the frames and sub- frames carrying the data packets or by identifying the frames and sub-frames that have been received as error. SUMMARY OF THE INVENTION The present invention proposes a system and method wherein the need to use the SCH, BCH or the reference signals is obviated. The proposed method suggests a unique and easy way to identify the Frame boundary in case of multiple identical/ non identical SCHs in different sub-frames using a new method which is called "sub frame position difference method". This method identifies the sub-frame id based on the number of symbol/ sub-frame difference between two sub-frames carrying the SCH symbol. The present invention proposes a method which identifies the position of a slot/ sub-frame or any data packet based on the different differences in between them. Further this invention proposes a system and method which can tell the slot/ sub- frame or any data packet identifier (id) based on the difference (in time or number of slots/ sub-frames or any data packets) between two subsequent slots/ sub- frames or any data packets which may be identical to each other. The invention relates to communication protocols and more particularly to communication protocols in Line Terminal Equipment (LTE). The different detection protocols available for radio frame timing detection are: Synchronization Channel (SCH) based detection; Broadest Channel (BCH) based detection, and Reference signal-based detection. The present invention provides a unique way of identifying the Frame boundaries in multiple identical/ non identical SCH's in different sub-frames via the use of a new method called "sub frame position difference method". The method implements the use of the differences between the different sub frames carried by the SCH. The sub frame identity and hence the frame boundary can be identified by calculating the difference between the positions (based on time or number of slots/ sub-frames or any data packets) of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other. Accordingly the invention explains a method for sub-frame id and frame boundary detection in LTE wherein the method implements the use of the differences between the different sub frames carried by the SCH whereby the sub frame identity and hence the frame boundary is identified by calculating the difference between the positions of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other. Accordingly the invention explains a system for sub-frame id and frame boundary detection in LTE wherein the system implements the use of the differences between the different sub frames carried by the SCH whereby the sub frame identity and hence the frame boundary is identified by calculating the difference between the positions of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other. 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 ACCOMPANYING DRAWINGS Figure 1 depicts SCH symbols equally spaced. It is not possible to tell which ones (sub-frame) is received if all the SCH symbols are identical. Figure 2 depicts Four SCH symbols placed in frame 1 4 10 17 with a position difference of (3, 6, 7, 4) between the subsequent SCH sub-frame. From the SCH carrying sub-frame position difference between two such sub-frames the sub- frame id (and therefore the Frame boundary) can be told precisely. DETAILED DESCRIPTION OF INVENTION The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. However, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore the details disclosed herein are not to be interpreted as limiting but merely as the basis for the claims and as a basis for teaching one skilled in the art how to make or use the invention. The LTE cell search procedure must get the synchronization both in time and frequency and should be able to detect the frame boundary (or alternatively the sub-frame id), to make complete sense of the subsequent information(s) in the downlink. The synchronization procedure is completed with the help of Synchronization Channel (SCH). SCH is carried in one or more sub-frames in an LTE system. A small number of SCH symbols per radio frame are desirable in order to reduce the overhead. Furthermore, from the viewpoint of the timing detection performance against noise and interference, the signal energy of the SCH should be concentrated on a small number of OFDM symbols. However, time diversity employing multiple SCH symbols is very effective in achieving fast cell search by improving the detection probability of the SCH particularly in a high mobility environment. Multiple SCH symbols per radio frame can also reduce the minimum required correlation detection period for SCH timing detection. Therefore, single or a few SCH symbol (typically two or four SCH symbols) mapping in a 10-msec radio frame is a promising structure as shown in as shown in the figure in section 5. So, most probably we would require more than 1 SCH symbol in one radio frame. These symbols will be located in different sub frames. The above requirement will impose the necessity to know the sub frame id in order to know the frame boundary. To explain, the UE receives a SCH sequence and it needs to know which sub frame is being transmitted currently. Say the SCH will be transmitted in sub frame 1, 6, 11 and 16 (figure 1); so the UE needs to know the sub frame to which the received SCH belongs then only it can determine the current frame position and the frame boundary. The present invention proposes following method to get the frame boundary: The sub frame id is explicitly signaled. It can be done using data bits in the SCH symbol which is not carrying the P-SCH. In case, SCH symbols transmitted on different sub frames are not identical, the UE will come to know of the sub frame id by using the corresponding (pre stored) mapping between the received SCH and the sub frame id. In case above signaling (point 1) is not possible (like data insertion in SCH symbols does not look a good option and may disturb any property (like time- domain symmetry) of the P-SCH) and more than one SCH transmitted are identical then the present invention proposes another scheme called "sub frame position difference method". Explanation of point 3: "sub frame position difference method": Frame Timing will be given by repeatability of SCH in a Frame i.e. will be given by how many time SCHs occur in a frame. Casel: One SCH per Frame -> Only one SCH will directly indicate the position in the frame. Case2: Two SCHs per Frame -> Frame boundary can be identified by repeating the SCH in any position except the one where in the distance between them (hereafter referred to as "position difference") is 20/2 = 10. To explain, it cannot place the first and the second SCH in 1st and 11th place. Any other position difference (1-9) is valid. Case3: Three SCHs per Frame -> The position difference pattern will define the Frame boundary. To explain, the position difference between any two subsequent SCH will not be a constant e.g. they can be arithmetically progressing. Let the position difference pattern be 1 3 6 i.e. the sub frame containing SCH are expected to be at one of these three out of 20 available sub frames. When a SCH sub frame is received then we wait for the next SCH sub frame and if the difference between these two is 2 then the first and the second SCH sub frame is received respectively; if the difference between these two is 3 then the 2nd and third SCH sub frame is received respectively; else (difference > 3) the 3rd SCH sub frame and the first sub-frame of the next frame is received respectively. Perhaps any position difference pattern will do but NOT the constant position difference pattern. The position difference pattern will be known in advance and will be unique. The above theory can be extended to n repeat SCHs in a Frame. Example: From figure '1': if the UE received a SCH sub-frame and received another SCH sub-frame after 5 sub-frames; it does not indicate anything about the sub-frames position (sub-frame id) as such. But from figure 'b' where Four SCH symbols are placed in frame 1 4 10 17: it can be told explicitly which SCH sub-frame was received prior to the current SCH sub- frame based on the number sub-frames received between them. For example if the sub-frame difference between 2 SCH sub-frames is 7 then the two SCH sub- frames are at position 10 and 17 respectively. To illustrate further the following combination are valid: 1 48 13-ok (3,4, 5, 8) 1 48 14-ok (3,4, 6, 7) 1 48 15-ok (3, 4, 7, 6) 1 48 16-ok (3,4, 8, 5) 1 49 17-ok (3, 5, 8,4) 14 10 17-ok (3, 6,7, 4) and following combinations are NOT valid: 1 49 15-Not possible (3, 5,6,6) 1 4 9 16 - Not possible (3, 5, 7, 5) 1 5 10 16 - not possible (4, 5, 6, 5) 1 5 10 17 - not possible (4, 5, 7, 4) 1 6 11 17 - not possible all equally spaced (5) 1 6 12 16 - not possible (5, 6, 4, 5) The combinations mentioned above are only a few of the valid/ not valid combinations. Also, to increase the probability of detection the SCH sub-frames should be as much equally spaced from each other as possible. Many combinations of SCH sub-frame position are possible but the one which retain the above property as much as possible (like 14 8 15) should be considered. 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. ADVANTAGES Easy detection of sub-frame id and frame boundary No additional overhead Precise detection with no false detection probability GLOSSARY OF TERMS AND DEFINITIONS THEREOF SCH Synchronization Channel We claim, 1. A method for sub-frame id and frame boundary detection in LTE wherein the method implements the use of the differences between the different sub frames carried by the SCH whereby the sub frame identity and hence the frame boundary is identified by calculating the difference between the positions of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other. 2. A method as claimed in claim 1 wherein the sub frame id is explicitly signalled or can be done using data bits in the SCH symbol which is not carrying the P- SCH. 3. A method as claimed in claiml wherein if, SCH symbols transmitted on different sub frames are not identical, the UE will come to know of the sub frame id by using the corresponding mapping between the received SCH and the sub frame id. 4. A system for sub-frame id and frame boundary detection in LTE wherein the system implements the use of the differences between the different sub frames carried by the SCH whereby the sub frame identity and hence the frame boundary is identified by calculating the difference between the positions of the two subsequent slots/ sub-frames or any data packets which may be even identical to each other. 5. A method for sub-frame id and frame boundary detection in LTE substantially described particularly with reference to the accompanying drawings. 6. A system for sub-frame id and frame boundary detection in LTE substantially described particularly with reference to the accompanying drawings.

Documents:

1518-CHE-2006 AMENDED CLAIMS 27-09-2013.pdf

1518-CHE-2006 AMENDED PAGES OF SPECIFICATION 27-09-2013.pdf

1518-CHE-2006 EXAMINATION REPORT REPLY RECEIVED. 27-09-2013.pdf

1518-CHE-2006 FORM-1 27-09-2013.pdf

1518-CHE-2006 FORM-13 27-09-2013.pdf

1518-CHE-2006 FORM-3 27-09-2013.pdf

1518-CHE-2006 OTHER PATENT DOCUMENT 27-09-2013.pdf

1518-CHE-2006 OTHERS 27-09-2013.pdf

1518-CHE-2006 POWER OF ATTORNEY 27-09-2013.pdf

1518-CHE-2006 ABSTRACT.pdf

1518-CHE-2006 CLAIMS.pdf

1518-CHE-2006 DESCRIPTION (COMPLETE).pdf

1518-CHE-2006 FORM-1.pdf

1518-CHE-2006 FORM-18.pdf

1518-CHE-2006 FORM-5.pdf

1518-CHE-2006 OTHER PATENT DOCUMENT. 27-09-2013.pdf

1518-che-2006-correspondnece-others.pdf

1518-che-2006-description(provisional).pdf

1518-che-2006-drawings.pdf

1518-che-2006-form 1.pdf

1518-che-2006-form 26.pdf