Title of Invention

METHOD FOR SELECTING AN ACCESS POINT FOR HANDOFF BASED ON DIRECTION OF MOVEMENT OF A MOBILE NODE

Abstract

This invention explains a method and system for network attachment for fast handoff using GPS in a communication system comprising plurality of cells wherein the said method comprising the steps of: calculating the positions using GPS at periodic time intervals and storing the said positions in its memory by a mobile node; calculating the direction of the movement of mobile node based on the said positions stored in the memory; finding the candidate access points which is having signal strength above a threshold value during handoff time; selecting the most eligible access point among the candidates by finding the nearest access point in the direction of the movement of the said mobile node; providing a hint to the fast handoff methods about the selected access point; and hinting the lower layers about the access point for association by the fast handoff methods.

Full Text

FIELD OF THE INVENTION The present invention in general relates to the mobility management. Particularly the present invention relates to a method and system for finding suitable access point/network point of attachment by mobile node during the handoff applicable for mobile nodes and network that supports mobility. DESCRIPTION OF THE RELATED ART 1. Handoff based on signal strength of access points In mobile radio communication systems, for instance mobile telephony systems such as GSM, UMTS etc, a mobile station is in radio contact with a base station in a set of base stations located around the mobile station. When the signal strength from the current base station is weakened due to movement of the mobile station a so called handoff to another base station in the set is performed. Normally handoff is done to that base station in the set that has the highest signal strength at the mobile station at the moment in question. This method, however, sometimes leads to a non-optimal choice of base station. Under certain circumstances it would be more advantages to choose another base station among the base stations in the set that have sufficiently high signal strength at the mobile station. 2. Handoff based on signal strength and loading factor of the access points Describes a system within which the mobile station performs handoff based on signal strength and loading factor. According to the invention there is provided a data communications network including a plurality of stationary access points and a plurality of mobile units, a mobile unit being capable of communicating with at least two access points in a predetermined range. The mobile unit associated with an access point and experiencing an unacceptably low communication level scans for the access points. The most eligible access point is selected according to the following criteria: (a) received access point signal quality (b) loading factor at the access point The mobile unit on scanning identifies all stationary access points with a signal quality at least equal to a predetermined threshold, and selects for association the most eligible one of the access points having the lowest loading factor, and in which, when a plurality of stationary access points has an equal lowest loading factor, the stationary access point having the highest received signal quality is selected. 3. Handoff based on the path followed by the mobile unit [1] Describes a method of handoff based on route followed by the mobile unit using historic data from previous handoffs along the specific route The method includes determining a route traveled by a mobile terminal in a mobile communication network by determining the geographic position of the mobile terminal at a plurality of time instants as the mobile terminal is moving within the network. The positions are stored in a memory, and a route is determined when a predetermined number of locations occur within a predetermined area. Once a route has been defined and the path of the mobile terminal has been determined to correspond to the route, the network may monitor handoffs occurring along the defined route. When a handoff occurs, the position of the mobile terminal at the time of the handoff is determined and stored in memory. Preferably for each handoff, a quality metric indicating handoff success or quality is determined and stored. The handoff success can be determined based on measurements such as the signal strength, bit error rate (BER), word error rate (WER), or other channel quality measurements before and after the handoff. Separate metrics can be computed for both the uplink and the downlink or a single metric can be computed that takes both uplink and downlink measurements into account. Once a quality metric is determined for a particular handoff position, the quality metric can be used to make future handoff decisions. Thus the information about the routes traveled by the mobile terminals and the location, success and access point for each handoff along the route is eventually gathered and stored. Subsequent mobile terminals moving through the network are monitored and their paths are compared with the predetermined routes. The mobile terminal is considered to be moving along the predetermined route when the path matches any of the predetermined routes. Information associated with the identified route may then be used to aid in one or more handoffs of the mobile terminal while traveling along the route. Thus based upon the historical information previously monitored by the network, a mobile terminal can be identified as moving along a pre-recognized route and appropriate handoff locations and access points can be determined to best maximize the handoff quality. 1. Next access point selection based on signal strength and loading factor may not give optimal choice all the times. In some circumstances, rapid handoffs may occur due to incorrect selection of access point that deteriorates the call quality and increases the load of the communication system. 2. The other method which describes handoff based on the path followed by the mobile unit requires eventual learning about each handoff and storing this information to assist in future handoffs. SUMMARY OF THE INVENTION It is an object of the present invention to provide a communication system and method allowing improved selection by a mobile unit of an access point for association, thus reducing the probability of frequent handoffs due to an erroneous handoff decision. It is a further object of the present invention to provide a method wherein the selection of access point is based on the direction of movement of the mobile unit and location information of the neighboring access points. Access point which is nearest to the path projected in the direction of movement of the mobile unit is selected as the appropriate one for handoff It is a further object of the present invention to incorporate certain functions into mobile station wherein the selected access point for handoff is provided as a hint to the fast handoff methods and fast handoff methods in turn hinting the lower layers about the access point to handoff This method proposes a method to find next Network Attachment by a Mobile Node when there are multiple Access Points to which it can be attached during handoff. It uses direction of the movement of Mobile Node and location information of the neighboring Access Points to find out the appropriate access point. This method provides a hint to the fast handoff methods about the suitable access point. Fast handoff methods in turn may hint the lower layers to which access point mobile node should handoff. GPS is used in this method for mobile nodes to calculate their direction of movement as well to find out the location of the Access Points. These and other objects, features and advantages of the present invention will become more readily apparent from the detailed description taken in conjunction with the drawings and the claims. Accordingly this invention explains a method for network attachment for fast handoff using GPS in a communication system comprising plurality of cells wherein the said method comprising the steps of: (a) calculating the positions using GPS at periodic time intervals and storing the said positions in its memory by a mobile node; (b) calculating the direction of the movement of mobile node based on the said positions stored in the memory; (c) finding the candidate access points which is having signal strength above a threshold value during handoff time; (d) selecting the most eligible access point among the candidates by finding the nearest access point in the direction of the movement of the said mobile node; (e) providing a hint to the fast handoff methods about the selected access point; and (f) hinting the lower layers about the access point for association by the fast handoff methods. Each access point is configured with the location information of the neighboring access points statically or dynamically. The mobile node gets the location information of the candidate access points from its serving access point. Selecting the most eligible access point among the candidate access points is done by calculating the length of perpendiculars from the location to the line projected in the direction of its movement. Selecting the most eligible access point among the candidate access points is done selecting the access point which has got least length of perpendicular from the location to the line projected in the direction of its movement. During the handoff time, GPS based movement detection system gets the candidate access points whose signal strength is above the threshold from lower layers. The said mobile node is adapted to receive predetermined signals from neighboring access points during the handoff time. Candidate access points for handoff have signal strengths above the said threshold value. The most eligible access point among the candidate access points is the nearest access point in the direction of the movement of the MN. Accordingly this invention also explains a system for network attachment for fast handoff using GPS in a communication system comprising plurality of cells wherein the said system comprising: (a) Means for calculating the positions using GPS at periodic time intervals and storing the said positions in its memory by a mobile node; (b) Means for calculating the direction of the movement of mobile node based on the said positions stored in the memory; (c) Means for finding the candidate access points which is having signal strength above a threshold value during handoff time; (d) Means for selecting the most eligible access point among the candidates by finding the nearest access point in the direction of the movement of the said mobile node; (e) Means for providing a hint to the fast handoff methods about the selected access point; and (f) Means for hinting the lower layers about the access point for association by the fast handoff methods. In the said system each access point is configured with the location information of the neighboring access points statically or dynamically. In the system the mobile node gets the location information of the candidate access points from its serving access point. Selecting the most eligible access point among the candidate access points is done by calculating the length of perpendiculars from the location to the line projected in the direction of its movement. Selecting the most eligible access point among the candidate access points is done selecting the access point which has got least length of perpendicular from the location to the line projected in the direction of its movement. In the system during the handoff time, GPS based movement detection system gets the candidate access points whose signal strength is above the threshold from lower layers . The said mobile node is adapted to receive predetermined signals from neighboring access points during the handoff time. Candidate access points for handoff have signal strengths above the said threshold value. The most eligible access point among the candidate access points is the nearest access point in the direction of the movement of the MN. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS Figure 1 shows a possible scenario where this invented method is applicable. Figure 2 shows a reference scenario for finding the nearest access point in the direction of movement of the mobile node. Figure 3 depicts the architecture of the proposed system within the mobile node. DETAILED DESCRIPTION OF THE INVENTION The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. The following description and drawings are illustrative of the invention and are not to be construed as limiting the innovation. Numerous specific details are described to provide a through understanding of the present invention. However in certain instances well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail. Figure. 1 depicts an example scenario where the proposed method is helpful. The communication system shown in figure. 1 comprises a plurality of access points. Each access point is located in, and provides service to, a geographic region referred to as cell. In general there is one access point for each cell. Within each cell, there may be a plurality of mobile nodes that communicate via radio link with the access point. The mobile node MN generally communicates with the access point in that cell in which it is currently located. As the mobile node MN travels from cell to cell, the communication from the access point AP in one cell is handed over to the access point AP in a neighboring cell. This procedure is called handoff. Figure 1 shows a possible scenario where this invented method is applicable. PAP is the access point with which MN is currently associated with. In this figure NAP1 and NAP2 are the possible neighboring access points with which MN may be associated. When signal strength from PAP gets weakened below a threshold value, MN starts finding the appropriate next access point for handoff using the method disclosed in the specification Fig. 1 shows a situation where it is better to associate to an access point in the direction of movement of the mobile node than to an access point that has strongest signal strength. In Fig.1 there are three access points PAP, NAP1, NAP2. A mobile station is assumed to be on its way from point A to point C over point B. At point A the mobile station is in contact with access point PAP. At point B the signal strength from access point PAP has weakened and neighboring access points has a significantly stronger signal, and therefore handoff is ordered. Since the mobile station continuously measures the signal strength from surrounding access points, it has been established in point B that access point NAP1 has the strongest signal strength, and therefore handoff in accordance with conventional methods is ordered to this access point. But the direction of the movement of the mobile node indicates that NAP2 is better choice than NAP1, If the conventional method is followed, as the mobile station then continues to point C the signal strength from access point NAP1 rapidly decreases and a new handoff has to be ordered. In this case handoff is made to access point NAP2. Thus, in the described situation a handoff decision in point B is very rapidly followed by a new handoff decision in point C. However, if access point NAP2 which is in the direction of movement of MN, already in point B has sufficient signal strength to take over the communication with the mobile station, it would be more suitable to order handoff already at that point to access point NAP2 instead of to access point NAP1. The present invention thus finds the appropriate access point for association based on the direction of the movement of the mobile node. The detailed operation of the invention is as follows: A mobile station is constructed to receive predetermined signals from neighboring access points during the handoff time. The access points that have signal strength above a threshold value are considered as candidate access points for handoff. In Fig.1, MN is getting signals from both NAP1 and NAP2 during handoff time. Assume both NAP1 and NAP2 have signal strength above the threshold thus making them appropriate candidates for handoff. The most eligible access point among these candidates is the nearest access point in the direction of the movement of the MN. MN finds its direction of movement during handoff time in the following manner: Using GPS, MN calculates its geographic position at periodic time intervals. It will store the positions in the memory and during handoff time, it will calculate the direction of movement based on the last 'n' positions (configurable) stored. Figure 2 shows a reference scenario for finding the nearest access point in the direction of movement of the mobile node. MN calculates the length of perpendiculars from the candidate access point positions to the line expanded in the direction of movement of MN. Appropriate access point is the one which has got least length of perpendicular. Referring to Fig.2 MN selects the most eligible access point in the following manner: ? For all the candidate access points, MN calculates the length of perpendiculars from their location to the line expanded in the direction of path of MN. ? Appropriate access point is the one which has got least length of perpendicular. ? In the fig.2, y1 and y2 are the length of perpendiculars from NAP1 and NAP2 respectively. ? Since y2 Thus MN detects the suitable access point in the direction of its movement. The method assumes that MN is provided with the location information of the neighboring access points. One of the methods to obtain this information is described below Each access point can be configured with the location information of the neighboring access points either statically or dynamically. MN can get the location information of the candidate access points from its serving access point. Figure 3 depicts the architecture of the proposed system within the mobile node GPS based movement detection system shown in the figure finds the appropriate next access point using the method disclosed in this specification. The obtained access point is given as a hint to the fast handoff methods. Fast handoff methods in turn may hint the lower layers (L2) about the possible access point for handoff. Fig.3 depicts the architecture of the proposed system. ? During the handoff time, GPS based movement detection system gets the candidate access points whose signal strength is above the threshold from lower layers (L2). It calculates the direction of movement of the mobile node, gets the location information of the candidate access points and finds the appropriate access point based on the method explained above. ? The selected access point is provided as a hint to the fast handoff methods. ? Fast handoff methods in turn may hint the lower layers (L2) about the access point for association The above-presented description is of the best mode contemplated for carrying out the present invention. The manner and process of making and using it is in such a full, clear, concise and exact terms as to enable to any person skilled in the art to which it pertains to make and use this invention. New embodiments in particular, which also lie within the scope of the invention can be created, in which different details of the different examples can in a purposeful way be combined with one another. This invention is however, susceptible to modifications and alternate constructions from that disclosed above which are fully equivalent. Consequently, it is not the intention to limit this invention to the particular embodiment disclosed. On the contrary, the intention is to cover all modifications and alternate constructions coming within the spirit and scope of the invention as generally expressed by the following claims which particularly point out and distinctly claim the subject matter of the invention. GLOSSARY OF THE TERMS AP : - Access Point MN : - Mobile Node NAP : - Next Access Point PAP : - Previous Access Point. GPS : - Global Positioning System L2 ; - Layer 2 (Data link layer/MAC layer) WE CLAIM 1. A method for network attachment for fast handoff using GPS in a communication system comprising plurality of cells wherein the said method comprising the steps of: (a) calculating the positions using GPS at periodic time intervals and storing the said positions in its memory by a mobile node; (b) calculating the direction of the movement of mobile node based on the said positions stored in the memory; (c) finding the candidate access points which is having signal strength above a threshold value during handoff time; (d) selecting the most eligible access point among the candidates by finding the nearest access point in the direction of the movement of the said mobile node; (e) providing a hint to the fast handoff methods about the selected access point; and (f) hinting the lower layers about the access point for association by the fast handoff methods. 2. A method as claimed in claim 1 wherein each access point is configured with the location information of the neighboring access points statically or dynamically. 3. A method as claimed in claim 1 wherein the mobile node gets the location information of the candidate access points from its serving access point. 4. A method as claimed in claim 1 wherein selecting the most eligible access point among the candidate access points is done By calculating the length or perpendiculars from the location to the line projected in the direction of its movement. 5. A method as claimed in claim 4 wherein selecting the most eligible access point among the candidate access points is done selecting the access point which has got least length of perpendicular from the location to the line projected in the direction of its movement. 6. A method as claimed in claim 1 wherein during the handoff time, GPS based movement detection system gets the candidate access points whose signal strength is above the threshold from lower layers . 7. A method as claimed in claim 1 wherein the said mobile station is adapted to receive predetermined signals from neighboring access points during the handoff time. 8. A method as claimed in claim 1 wherein candidate access points for handoff have signal strengths above the said threshold value. 9. A method as claimed in claim 1 wherein the most eligible access point among the candidate access points is the nearest access point in the direction of the movement of the MN. 10. A system for network attachment for fast handoff using GPS in a communication system comprising plurality of cells wherein the said system comprising: (a) Means for calculating the positions using GPS at periodic time intervals and storing the said positions in its memory by a mobile node; (b) Means for calculating the direction of the movement of mobile node based on the said positions stored in the memory; (c) Means for finding the candidate access points which is having signal strength above a threshold value during handoff time; (d) Means for selecting the most eligible access point among the candidates by finding the nearest access point in the direction of the movement of the said mobile node; (e) Means for providing a hint to the fast handoff methods about the selected access point; and (f) Means for hinting the lower layers about the access point for association by the fast handoff methods. 11. A system as claimed in claim 10 wherein each access point is configured with the location information of the neighboring access points statically or dynamically. 12. A system as claimed in claim 10 wherein the mobile node gets the location information of the candidate access points from its serving access point. 13. A system as claimed in claim 10 wherein selecting the most eligible access point among the candidate access points is done by calculating the length of perpendiculars from the location to the line projected in the direction of its movement. 14. A system as claimed in claim 13 wherein selecting the most eligible access point among the candidate access points is done selecting the access point which has got least length of perpendicular from the location to the line projected in the direction of its movement. 15. A system as claimed in claim 10 wherein during the handoff time, GPS based movement detection system gets the candidate access points whose signal strength is above the threshold from lower layers . 16. A system as claimed in claim 10 wherein the said mobile station is adapted to receive predetermined signals from neighboring access points during the handoff time. 17. A system as claimed in claim 10 wherein candidate access points for handoff have signal strengths above the said threshold value. 18. A system as claimed in claim 10 wherein the most eligible access point among the candidate access points is the nearest access point in the direction of the movement of the MN. 19. A method for network attachment for fast handoff using GPS substantially as herein described particularly with reference to the drawings. 20. A system for network attachment for fast handoff using GPS substantially as herein described particularly with reference to the drawings.

Documents:

1972-CHE-2005 AMENDED PAGES OF SPECIFICATION 15-04-2013.pdf

1972-CHE-2005 AMENDED CLAIMS 15-04-2013.pdf

1972-CHE-2005 CORRESPONDENCE OTHERS 15-04-2013.pdf

1972-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 01-03-2013.pdf

1972-CHE-2005 FORM-1 01-03-2013.pdf

1972-CHE-2005 FORM-13 01-03-2013.pdf

1972-CHE-2005 OTHER PATENT DOCUMENT 01-03-2013.pdf

1972-CHE-2005 POWER OF ATTORNEY 15-04-2013.pdf

1972-CHE-2005 AMENDED CLAIMS 01-03-2013.pdf

1972-CHE-2005 AMENDED PAGES OF SPECIFICATION 01-03-2013.pdf

1972-CHE-2005 FORM-1 01-03-2013.pdf

1972-CHE-2005 FORM-13 19-06-2006.pdf

1972-CHE-2005 POWER OF ATTORNEY 01-03-2013.pdf

1972-che-2005-abstract.pdf

1972-che-2005-claims.pdf

1972-che-2005-correspondnece-others.pdf

1972-che-2005-description(complete).pdf

1972-che-2005-drawings.pdf

1972-che-2005-form 1.pdf

1972-che-2005-form 13.pdf

1972-che-2005-form 26.pdf