WO2015084153A1

WO2015084153A1 - System and method for a handover in a wireless network

Info

Publication number: WO2015084153A1
Application number: PCT/MY2014/000194
Authority: WO
Inventors: Hasbullah Bin Mazlan Mohammad; Haseeb Shariq; Abobakr Ahmed Balfaqi Mohammad; Sivanand Sridhar
Original assignee: Mimos Berhad
Priority date: 2013-12-05
Filing date: 2014-06-26
Publication date: 2015-06-11

Abstract

The present invention relates to a system (100) and method for reducing handover latency in a wireless network. The system (100) comprises of at least one mobile node (200); at least one access point (AP) (300); at least one access controller (AC) (400) connected to the AP (300); at least one other neighbour AC (500); and at least one other neighbour AP (600). The system (100) is further characterised in that at least one Received Signal Strength (RSS) Checker module (10), at least one Moving Weight Discovery (MWD) module (20), at least one Client Movement Prediction (CMP) module (30) and at least one Access Controller Context Manager (ACCM) module (40).

Description

SYSTEM AND METHOD FOR A HANDOVER IN A WIRELESS NETWORK

FIELD OF INVENTION

The present invention relates to a system and method for reducing handover latency in a wireless network.

BACKGROUND OF THE INVENTION

Roaming can cause higher handover latency as mobile terminals disconnect abruptly from the previous Access Point (AP) to connect to a new AP. Higher handover latency causes service interruption to users who use the Real- Time Application (RTA). To connect to a new AP, mobile users have to scan for the new AP before re-authenticate with the AP.

There are three phases in the re-authentication operation which are the authentication and association phase, the 802.1x authentication phase and the 4- way handshake phase. The high latency of the re-authentication operation causes the mobile users to take a longer time to connect to a new AP. This will cause a higher handover latency and an increase of packet loss. Consequently, this will affect the performance of the RTA.

To reduce the handover latency in 802.1x authentication phases which has higher latency compared to other phases of the re-authentication operation, context transfer methods have been introduced. However, in the existing context transfer methods the AP still receives the context cache even without roaming. This results in in high memory usage in the AP which affects the efficiency of the network performance.

Apart from that, in the existing handover decision, there is a probability for handover failure and unnecessary handover during roaming in Wireless Local Area Network (WLAN) due to inaccurate prediction and decision. There is still no accurate mechanism to determine when a mobile node will move from one AP to another, thus leading to a slow handover and performance degradation in RTA's services for users during roaming. Therefore, there is a need to provide a system and method that addresses the above drawbacks. SUMMARY OF INVENTION

The present invention relates to a system and method for a handover in a wireless network. The system according to a first embodiment of the present invention is characterised by at least one mobile node (200a); at least one access point (AP) (300a); at least one access controller (AC) (400a); at least one neighbour access controller (AC) (500a); and at least one neighbour access point (AP) (600a), wherein the system (100a) is further characterised in that the at least one access point (300a) includes at least one Received Signal Strength (RSS) Checker module (10a) for checking the RSS of the at least one mobile node (200a), at least one Moving Weight Discovery (MWD) module (20a) for randomly collecting and analysing the boundary for Moving Weight to predict the movement of the at least one mobile node (200a), and at least one Client Movement Prediction (CMP) module (30a) for collecting and analysing the rate of movement of the mobile node (200a) based on the pattern of the change in the signal strengths of the mobile node (200a); the at least one access controller (400a) includes at least one Access Controller Context Manager (ACCM) module (40a) for managing the context cache and transferring the context cache either to neighbour APs (600a) under the control of the current AC (400a) or to the neighbour AC (500a). Preferably, the at least one Moving Weight Discovery (MWD) module (20a) further includes at least one MWD Received Signal Strength (RSS) Collector (21a) for calculating Moving Weight of the AP (300a); at least one MW Calculator (22a) for calculating the average value of rate of change of RSS; and at least one MW Database (23a) for storing the Moving Weight of at least one AP (300a).

Preferably, the at least one Client Movement Prediction (CMP) module (30a) further includes at least one CMP Received Signal Strength (RSS) Collector (31a) for collecting data to predict the movement of the mobile node (200a); at least one Pattern Decision (32a) for determining the rate of change of movement of the mobile node (200a); and at least one Moving Weight (MW) Decision (33a) for predicting the movement status of the mobile node (200a).

The system (100b) for a handover in a wireless network according to a second embodiment of the present invention is characterised by at least one mobile node (200b); at least one access point (AP) (300b); at least one access controller (AP) (400b); at least one neighbour access controller (AC) (500b); and at least one neighbour access point (AP) (600b), wherein the system (100b) is further characterised in that the at least one access point (300b) includes at least one Received Signal Strength (RSS) Checker module (10b) for checking the RSS of the at least one mobile node (200b), the at least one access controller (400b) includes at least one Moving Weight Discovery (MWD) module (20b) for randomly collecting and analysing the boundary for Moving Weight which is used in predicting the movement of the at least one mobile node (200b), at least one Client Movement Prediction (CMP) module (30b) for collecting and analysing the rate of movement of the mobile node (200b) based on the pattern of the change in the signal strengths of the mobile node (200b), and at least one Access Controller Context Manager (ACCM) module (40b) for managing the context cache and transferring the context cache to either neighbour APs (600b) under the control of the current AC (400b) or to the neighbour AC (500b).

Preferably, the at least one Moving Weight Discovery (MWD) module (20b) further includes at least one MWD Received Signal Strength (RSS) Collector (21b) for calculating Moving Weight of the AP (300b); at least one MW Calculator (22b) for calculating the average value of rate of change of RSS; and at least one MW Database (23b) for storing the Moving Weight of the at least on AP (300b).

Preferably, the at least one Client Movement Prediction (CMP) module (30b) further includes at least one CMP Received Signal Strength (RSS) Collector (31b) for predicting the movement of the mobile node (200b); at least one Pattern Decision (32b) for determining the rate of change of movement of the mobile node (200b); and at least one Moving Weight (MW) Decision (33b) for predicting the movement status of the mobile node (200b) either leaving the current AP (300b), moving towards the AP (300b) or if the mobile node (200b) is in a stationary mode. The method for a handover in a wireless network comprises the steps of connecting the mobile node (200) to the AP (300); determining the RSS of the mobile node (200) by the RSS Checker module (10); encapsulating the RSS of the mobile node (200) in a data packet by the RSS Checker module (10); sending the encapsulated data to the AC (400) by the RSS Checker module (10); forwarding the RSS information of mobile node (200) to the MWD module (20) and CMP module (30) which are implemented in the AP (300); determining Moving Weight by the MWD module (20); predicting the movement of the mobile node (200) by the CMP module (30); informing ACCM module (40) about the status of the mobile node (200) for the respective AP (300) by the CMP module (30); checking if all neighbour APs (600) are under its control by using the Neighbour Graph (42) by the ACCM Manager (41); and informing the ACCM Database (43) to send context cache to all neighbour APs (600) by the ACCM Manager (41) if neighbour APs (600) are under its control.

Preferably, determining Moving Weight by the MWD module (20) includes the steps of collecting the RSS of the mobile node (200) for a period of time by the MWD RSS Collector (21); calculating the rate movement of mobile node (200) for a certain period of time by the MW Calculator (22); determining whether the average rate of change of RSS is below a user defined threshold value; calculating upper and lower boundary values of the collected RSS of the mobile node (200) by the MW Calculator (22) if the average value rate of change of RSS is below the user defined threshold; averaging the upper and lower bound values based on a current value of Moving Weight to get a new value of Moving Weight; and forwarding the new value of Moving Weight to the CMP module (30) for the mobile node's (200) movement predicting process.

Preferably, predicting the movement of the mobile node (200) by the CMP module (30) includes the steps of collecting the RSS of the mobile node (200) for a period of time by the CMP RSS Collector (31); calculating the rate movement of the mobile node (200) for a period of time by the Pattern Decision (32); determining if the RSS values of the mobile node (200) is below a user defined threshold values by the MW Decision (33); and comparing the rate movement of the mobile node (200) with the values of the Moving Weight if the RSS values are below the defined threshold values to determine whether the mobile node (200) is leaving the current AC (400). Preferably, if neighbour APs (600a) are not under the ACCM Manager's (41a) control, the method includes the steps of broadcasting a message to determine the neighbour AC (500a) that manages the neighbour AP (600a) by the ACCM Manager (41a); replying to the broadcasted message if the neighbour APs (600a) are under its control by the neighbour AC (500a); informing the ACCM Database (43a) to forward the context cache to the neighbour AC (500a) by the ACCM Manager (41a) upon receiving the reply; and sending the context cache to the neighbour APs (600a) by the neighbour AC (500a).

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates a block diagram of a system (100a) for a handover in a wireless network according to a first embodiment of the present invention.

FIG. 2 illustrates a block diagram of a system (100b) for a handover in a wireless network according to a second embodiment of the present invention. FIG. 3 illustrates a flow chart of a method for a handover in a wireless network according to an embodiment of the present invention.

FIG. 4 illustrates a flow chart of the substeps of determining Received Signal Strength (RSS) of a mobile node (200).

FIG. 5 illustrates a flow chart of the substeps of determining Moving Weight.

FIG. 6 illustrates a control system flow of Moving Weight Discovery (MWD) module (20a, 20b) of FIG. 1 and FIG. 2.

FIG. 7 illustrates a flow chart of the substeps of predicting the movement of the mobile node (200).

FIG. 8 illustrates a control system flow of Client Movement Prediction (CMP) module (30a, 30b) of FIG. 1 and FIG. 2.

FIG. 9 illustrates a flow chart of the process flow for the ACCM module (40a, 40b) of FIG. 1 and FIG. 2. DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

Reference is made initially to FIG. 1 which illustrates a system (100a) for a handover in a wireless network according to a first embodiment of the present invention. The system (100a) comprises of a mobile node (200a), an AP (300a), an AC (400a), a neighbour AC (500a) and at least one neighbour AP (600a). The mobile node (200a) is connected to the AP (300a), wherein the AP (300a) comprises of at least one Received Signal Strength (RSS) Checker module (10a); at least one Moving Weight Discovery (WMD) module (20a); and at least one Client Movement Prediction (CMP) module (30a). The MWD module (20a) further comprises of an MWD Received Signal Strength (RSS) Collector (21a); a Moving Weight (MW) Calculator (22a) and a Moving Weight (MW) Database (23a), while the CMP module (30a) further comprises of a CMP Received Signal Strength (RSS) Collector (31a); a Pattern Decision (32a); and an MW Decision (33a). The AP (300a) is also connected to the AC (400a), wherein the AC (400a) comprises of an AC Context Manager (ACCM) module (40a) which further comprises in that an ACCM Manager (41a), a Neighbour Graph (42a) and an ACCM Database (43a). The AC (400a) is also connected to the Neighbour AC (500a) and to the at least one neighbour AP (600a).

The function of the RSS Checker module (10a) is for checking the RSS of the mobile node (200a) from the mobile node's (200a) data packet.

The MWD module (20a) is for randomly collecting and analysing the boundary for Moving Weight, which is used for predicting the movement status of the mobile node (200a). The MWD RSS Collector (21a) is an RSS aggregator for calculating the Moving Weight of the AP (300a). The RSS of the mobile node (200a) is collected randomly for some period of time. The MW Calculator (22a) is used to calculate the average value of rate of change of RSS by using the collected RSS of the mobile node (200a) in the MWD RSS Collector (21a). The upper and lower bound values of the RSS are calculated using the mean and standard deviation of the average value of rate of change of the mobile node's (200a) RSS in getting the value of Moving Weight. The MW Database (23a) is for storing the Moving Weight for all the APs (300a) under AC's (400a) control. Moreover, the MW Database (23a) is also used for averaging the new and old Moving Weight to optimize the Moving Weight that is to be used for the CMP module (30a).

The CMP module (30a) is for collecting and analysing the rate of movement of the mobile node (200a) based on the pattern of the change in the signal strengths of the mobile node (200a). The CMP RSS Collector (31a) is an aggregator for collecting data to predict the movement of the mobile node (200a). The RSS of the mobile node (200a) is collected when there is an uplink or a downlink transmission between the mobile node (200a) and the AP (300a). The RSS is collected for a period of time as long as there is a transmission. The Pattern Decision (32a) is used to determine the rate of change of movement of the mobile node (200a) using the gradient of the collected RSS of the mobile node (200a) by the CMP RSS Collector (31a). The MW Decision (33a) is used to predict the movement status of the mobile node (200a) either leaving the current AP (300a), moving towards the AP (300a) or if the mobile node (200a) is in a stationary mode. The value of handover threshold and Moving Weight is used for the handover prediction. The function of the ACCM module (40a) is for managing the context cache between APs (300a, 600a) and other neighbour AC (500a). The ACCM Manager (41a) handles the communication between current AC (400a) with other neighbour ACs (500a) to find neighbour APs (600a). The neighbour APs (600a) are checked between the current AC (400a) and other neighbour ACs (500a) by using the Neighbour Graph (42a). Finally, the ACCM Database (43a) is a database that holds the context cache for the active mobile nodes (200a) for fast handover process. The ACCM Database (43a) exchanges the context cache from current AC (400a) with neighbour AC (500a) based on potential neighbour APs (600a) by using the neighbour graph method.

Referring now to FIG. 2, it illustrates a system (100b) for a handover in a wireless network according to a second embodiment of the present invention. Similar to the system (100a) shown in FIG. 1 , the system (100b) in FIG. 2 also comprises of a mobile node (200b), an AP (300b), an AC (400b), a neighbour AC (500b) and at least one neighbour AP (600b). The mobile node (200b) is connected to the AP (300b), wherein the AP (300b) comprises of an RSS Checker module (10b). The AP (300b) is also connected the AC (400b), wherein the AC (400b) comprises of at least one Moving Weight Discovery (MWD) module (20b); at least one Client Movement Prediction (CMP) module (30b); and at least one Access Controller Context Manager (ACCM) module (40b). Similar to the system (100a) in FIG. 1, the MWD module (20bb) further comprises of an MWD RSS Collector (21a); an MW Calculator (22b); and an MW Database (23b), while the CMP module (30b) further comprises of a CMP RSS Collector (31b); a Pattern Decision (32b); and an MW Decision (33b). The ACCM module (40b) also similarly further comprises of an ACCM Manager (41b); a Neighbour Graph (42b); and an ACCM Database (43b). The AC (400b) is also connected to the Neighbour AC (500b) and to the at least one neighbour AP (600b).

The function of the RSS Checker module (10b) is for checking the RSS of the mobile node (200b) from the mobile node's (200b) data packet.

The MWD module (20b) is for randomly collecting and analysing the boundary for Moving Weight, which is used for predicting the movement status of the mobile node (200b). The MWD RSS Collector (21b) is an RSS aggregator for calculating the Moving Weight of the AP (300b). The RSS of the mobile node (200b) is collected randomly for some period of time. The MW Calculator (22b) is used to calculate the average value of rate of change of RSS by using the collected RSS of the mobile node (200b) in the MWD RSS Collector (21b). The upper and lower bound values of the RSS are calculated using the mean and standard deviation of the average value of rate of change of the mobile node's (200b) RSS in getting the value of Moving Weight. The MW Database (23b) is for storing the Moving Weight for all the APs (300b) under AC's (400b) control. Moreover, the MW Database (23b) is also used for averaging the new and old Moving Weight to optimize the Moving Weight that is to be used for the CMP module (30b). The CMP module (30b) is for collecting and analysing the rate of movement of the mobile node (200b) based on the pattern of the change in the signal strengths of the mobile node (200b). The CMP RSS Collector (31b) is an aggregator for collecting data to predict the movement of the mobile node (200b). The RSS of the mobile node (200b) is collected when there is an uplink or a downlink transmission between the mobile node (200b) and the AP (300b). The RSS is collected for a period of time as long as there is a transmission. The Pattern Decision (32b) is used to determine the rate of change of movement of the mobile node (200b) using the gradient of the collected RSS of the mobile node (200b) by the CMP RSS Collector (31b). The MW Decision (33b) is used to predict the movement status of the mobile node (300b) either leaving the current AP (300b), moving towards the AP (300b) or if the mobile node (200b) is in a stationary mode. The value of handover threshold and Moving Weight is used for the handover prediction.

The function of the ACCM module (40b) is for managing the context cache between APs (300b, 600b) and other neighbour AC (SOOb). The ACCM Manager (41 b) handles the communication between current AC (400b) with other neighbour ACs (500b) to find neighbour APs (600b). The neighbour APs (600b) are checked between the current AC (400b) and other neighbour ACs (500b) by using the Neighbour Graph (42b). Finally, the ACCM Database (43b) is a database that holds the context cache for the active mobile nodes (200b) for fast handover process. The ACCM Database (43b) exchanges the context cache from current AC (400b) with neighbour AC (500b) based on potential neighbour APs (600b) by using the neighbour graph method. Moving on to FIG. 3, it shows a flow chart of an overall process for a handover in a wireless network by using the system as shown in FIG. 1 or FIG. 2. Initially, the mobile node (200) connects to an AP (300) as in step 710. All packets and messages from different mobile nodes (200) enter the AP (300) through the Network Interface Card (NIC) as shown in FIG. 6. These packets and messages then go through the first phase which is to examine the RSS of the mobile node (200) using the RSS Checker (10). The AP (300) determines the mobile node's (200) RSS with the help of the RSS Checker module (10) as in step 720. The RSS Checker module (10) encapsulates the mobile node's (200) RSS in a data packet and sends the encapsulated data to the AC (400) as in step 730 besides forwarding the RSS information of the mobile node (200) to the MWD module (20) and CMP module (30) which can either be implemented in the AP (300) or AC (400) as in step 740. The MWD module (20) determines the Moving Weight as in step 750 before the CMP module (30) predicts the movement of the mobile node (200) as in step 760. The step of determining the RSS of the mobile node (200) by the RSS Checker module (10) is further explained in FIG. 4. Initially, the RSS Checker module (10) is initialized by starting the RSS checker service as in step 721 by receiving packets from the mobile node (200) wirelessly. There are 2 types of communications in real time communication which are a two-way communication such as VoIP and Video Conference and a one-way communication such as video streaming. For a two-way communication, there are an uplink communication from the mobile node (200) to the AP (300) and also a downlink communication from the AP (300) to the mobile node (200). On the other hand, for a one-way communication, there is only a downlink communication. After receiving packets from the mobile node (200) as in step 721 , the RSS Checker module (10) then determines whether or not there is an uplink connection from the mobile node (200) by the RSS Checker module (10) in the AP (300) as in step 722. If there is an uplink transmission from the mobile node (200), the RSS Checker module (10) extracts the mobile node's (200) RSS from the mobile node's (200) uplink data packet as in decision 723 before it proceeds to step 730 which is to encapsulate the RSS of the mobile node (200) in data packet. However, if there is no uplink transmission, the RSS Checker module (10) then determines whether or not there is a downlink transmission to the mobile node (200) as in step 724. If there is a downlink transmission to the mobile node (200), the RSS Checker module (10) extracts the RSS of the mobile node (200) from the Acknowledgement (ACK) message of the mobile node (200) as in step 725 before proceeding to the step of encapsulating the RSS information. On the other hand, if there is no downlink transmission to the mobile node (200), the RSS Checker module (10) directly encapsulates the RSS of the mobile node (200) in the data packet.

A flow chart for the process of determining the Moving Weight by the MWD module (20) is shown in FIG. 5 while the flow of the control system for the MWD module (20) is show in FIG. 6. Moving Weight is a boundary for the limit to determine either the mobile node (200) is leaving or entering the current network or in static position. Moving Weight is denominated by the Moving Weight In (MW|) and Moving Weight Out (MW₀) having the following correlation:

Θ > MW, ; mobile node is entering

Θ = MW₀≤ Θ≤ ; mobile node is static

MW₀ < Θ ; mobile node is leaving Initially, after the RSS of the mobile node (200) is examined using the RSS

Checker (10), the MWD RSS Collector (21) collects the RSS (s^ s₂ s_t1) of the mobile node (200) for a period of time (t,) as in step 751. The collected RSS (s^ s₂, s_ti) of the mobile node (200) then undergo a calculation process to define the rate movement (Θ) of mobile node (200) in dBm/s for a certain period of time (t^. This process is done by using the gradient of the collected RSS (Si, s₂, Sn) of the mobile node (200) as in step 752 by using an MW Calculator (22). This process is repeated periodically when a mobile node (200) is available in the system (100) for a certain period of time (ti). The data is collected continuously for the period of time (ti) despite the mobile node (200) is moving or static.

The MW Calculator (22) determines whether or not the average rate of change of RSS is below a user defined threshold value as in step 753. If the average value rate of change of RSS is above the threshold value, the process straightaway proceeds to step 760, wherein predicting the mobile node's (200) movement by the CMP module (30). On the other hand, if the average value rate of change of RSS is below the user defined threshold value, the MW Calculator (22) calculates the upper boundary (UP) and lower boundary (LB) values using the mean and standard deviation for gradient of the collected RSS of the mobile node (200) as in step 753 and decision 754. Based on a current value of Moving Weight, the current value for MW_t and MW₀ are averaged with the lower boundary (LB) and upper boundary (UP) to get the new value of Moving Weight as in step 755. Finally, the MW Database (23) forwards the new value of MW| and MW₀ to the CMP module (30) for the mobile node's (200) movement predicting process as in step 766.

The process of predicting the movement of the mobile node (200) by the CMP module (30) is further explained in a flow chart illustrated in FIG. 7 while the flow of the control system for CMP module (30) is illustrated in FIG. 8. Initially, after the RSS of the mobile node (200) is examined using the RSS Checker (10), the CMP RSS Collector (31) collects the RSS (Si._a,■■■■ s^₂, s_M, s,) of the mobile node (200) for a period of time (t₂) as in step 761. The collected RSS (s_i-t2 S_H2, S , S,) of the mobile node (200) undergo a calculation process by the Pattern Decision (32) to define the rate movement (Θ) of the mobile node (200) for a period of time (t₂) using the gradient of the collected RSS (si-t2, si-2, si-1 , si) as in step 762. This process can either be repeated every second or be repeated based on user defined time for the handover prediction.

Next, the MW Decision (33) determines if the RSS values (s_M, s _2l Su , Si) of the mobile node (200) is below a user defined threshold values as in step 763. The MW Decision (33) operates 2 separate processes which are an RSS Comparator process and a Rate Movement Comparator process. The values for the current RSS (Si-u,■■· , s ₂, Sj-i , Si) of the mobile node (200) and the rate movement (Θ) of the mobile node (200) undergo the RSS Comparator process and Rate Movement Comparator process respectively. The RSS Comparator module is to compare the current RSS values (s^, ■ · · , s>-₂, s^, Sj) of the mobile node (200) with the values of defined RSS threshold for handover as shown in FIG. 8, while the Rate Movement Comparator module is to compare the rate movement (Θ) of the mobile node (200) with the Moving Weight values in predicting the movement status of the mobile node (200). If the RSS values (s_i-t2 s_i-2, s_M, s are above the defined threshold values, the CMP

RSS Collector (31) repeats the step of collecting the RSS (s^, s«, Sn , si) of the mobile node (200) for a period of time (t₂) from step 761.

However, if the RSS values (s _a, ■■■· Sj._2l Sn , Sj) are below the defined threshold values, the rate movement (Θ) of the mobile node (200) is then compared with the values of the Moving Weight which is calculated using the MWD module (20) to determine whether the mobile node (200) is leaving the current AC (400) as in decision 764. This movement status of the mobile node (200) is predicted based on the results from RSS Comparator module and Rate Movement Comparator module. If the mobile node (200) is not leaving the current AC (400), the CMP RSS Collector (31) once again repeats the step of collecting the RSS (s_ht2, .... s^₂, s-_h1, s,) of the mobile node (200) for a period of time (t₂) as in step 761. On the other hand, if the mobile node (200) is leaving the current AC (400), the MW Decision (33) informs the ACCM module (40) about the status of the mobile node (200) for the respective AP (300) for performing the context transfer process as in decision 765.

Moving on to FIG. 9, it illustrates the final process of the fast handover in a wireless system according to the embodiment of the present invention which is the process flow for the ACCM module (40). The process starts with the ACCM Manager (41) checking if all neighbour APs (600) are under its control by using the Neighbour Graph (42) as in step 771. If the neighbour APs (600) are under its control, the ACCM Manager (41) then informs the ACCM Database (43) to finally send the context cache to all the neighbour APs (600) as in decision 772. However, if the neighbour APs (600) are not under its control, the ACCM Manager (41) will broadcast a message to determine the neighbour AC (500) that manages the neighbour AP (600) as in decision 773. The neighbour AC (500) then replies to the broadcasted message if the neighbour APs (600) are under its control as in step 774. Upon receiving the reply, the ACCM Manager (41) informs the ACCM Database (43) to forward the context cache to the neighbour AC (500) as in step 775. Finally, after receiving the context cache from the ACCM module (40), the neighbour AC (500) sends the context cache to the neighbour APs (600) as in step 776.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

A system (100a) for a handover in a wireless network is characterised by: a) at least one mobile node (200a);

b) at least one access point (AP) (300a);

c) at least one access controller (AC) (400a);

d) at least one neighbour access controller (AC) (500a); and

e) at least one neighbour access point (AP) (600a),

wherein the system (100a) is further characterised in that

a) the at least one access point (300a) includes:

i. at least one Received Signal Strength (RSS) Checker module (10a) for checking the RSS of the at least one mobile node (200a),

ii. at least one Moving Weight Discovery (MWD) module (20a) for randomly collecting and analysing the boundary for Moving Weight to predict the movement of the at least one mobile node (200a), and iii. at least one Client Movement Prediction (CMP) module (30a) for collecting and analysing the rate of movement of the mobile node (200a) based on the pattern of the change in the signal strengths of the mobile node (200a); and

b) the at least one access controller (400a) includes:

i. at least one Access Controller Context Manager (ACCM) module (40a) for managing the context cache and transferring the context cache either to neighbour APs (600a) under the control of the current AC (400a) or to the neighbour AC (500a).

The system (100a) as claimed in claim 1 , wherein the at least one Moving Weight Discovery (MWD) module (20a) further includes:

a) at least one MWD Received Signal Strength (RSS) Collector (21a) for calculating Moving Weight of the AP (300a);

b) at least one MW Calculator (22a) for calculating the average value of rate of change of RSS; and

c) at least one MW Database (23a) for storing the Moving Weight of the at least one AP (300a).

The system (100a) as claimed in claim 1 , wherein the at least one Client Movement Prediction (CMP) module (30a) further includes: a) at least one CMP Received Signal Strength (RSS) Collector (31a) for collecting data to predict the movement of the mobile node (200a); b) at least one Pattern Decision (32a) for determining the rate of change of movement of the mobile node (200a); and

c) at least one Moving Weight (MW) Decision (33a) for predicting the movement status of the mobile node (200a).

A system ( 00b) for a handover in a wireless network is characterised by: a) at least one mobile node (200b);

b) at least one access point (AP) (300b);

c) at least one access controller (AP) (400b);

d) at least one neighbour access controller (AC) (500b); and

e) at least one neighbour access point (AP) (600b),

wherein the system (100b) is further characterised in that

a) the at least one access point (300b) includes:

i. at least one Received Signal Strength (RSS) Checker module (10b) for checking the RSS of the at least one mobile node (200b); and

b) the at least one access controller (400b) includes:

i. at least one Moving Weight Discovery (MWD) module (20b) for randomly collecting and analysing the boundary for Moving Weight which is used in predicting the movement of the at least one mobile node (200b),

ii. at least one Client Movement Prediction (CMP) module (30b) for collecting and analysing the rate of movement of the mobile node (200b) based on the pattern of the change in the signal strengths of the mobile node (200b), and

iii. at least one Access Controller Context Manager (ACCM) module (40b) for managing the context cache and transferring the context cache to either neighbour APs (600b) under the control of the current AC (400b) or to the neighbour AC (500b).

5. The system (100b) as claimed in claim 4, wherein the at least one Moving Weight Discovery (MWD) module (20b) further includes: a) at least one MWD Received Signal Strength (RSS) Collector (21 b) for calculating Moving Weight of the AP (300b);

b) at least one MW Calculator (22b) for calculating the average value of rate of change of RSS; and

c) at least one MW Database (23b) for storing the Moving Weight of the at least one AP (300b).

The system (100b) as claimed in claim 4, wherein the at least one Client Movement Prediction (CMP) module (30b) further includes:

a) at least one CMP Received Signal Strength (RSS) Collector (31b) for collecting data to predict the movement of the mobile node (200b); b) at least one Pattern Decision (32b) for determining the rate of change of movement of the mobile node (200b); and

c) at least one Moving Weight (MW) Decision (33b) for predicting the movement status of the mobile node (200b) either leaving the current AP (300b), moving towards the AP (300b) or if the mobile node (200b) is in a stationary mode.

A method for a handover in a wireless network by using the system (100) as claimed in any of the preceding claims comprises the steps of:

a) connecting the mobile node (200) to the AP (300);

b) determining the RSS of the mobile node (200) by the RSS Checker module (10);

c) encapsulating the RSS of the mobile node (200) in a data packet by the RSS Checker module (10);

d) sending the encapsulated data to the AC (400) by the RSS Checker module (10);

e) forwarding the RSS information of mobile node (200) to the MWD module (20) and CMP module (30) which are implemented in the AP (300);

f) determining Moving Weight by the MWD module (20);

g) predicting the movement of the mobile node (200) by the CMP module (30);

h) informing ACCM module (40) about the status of the mobile node (200) for the respective AP (300) by the CMP module (30); i) checking if all neighbour APs (600) are under its control by using the Neighbour Graph (42) by the ACCM Manager (41); and

j) informing the ACCM Database (43) to send context cache to all neighbour APs (600) by the ACCM Manager (41) if neighbour APs (600) are under its control.

The method as claimed in claim 7, wherein determining Moving Weight by the MWD module (20) includes the steps of:

a) collecting the RSS of the mobile node (200) for a period of time by the MWD RSS Collector (21);

b) calculating the rate movement of mobile node (200) for a certain period of time by the MW Calculator (22);

c) determining whether the average rate of change of RSS is below a user defined threshold value;

d) calculating upper and lower boundary values of the collected RSS of the mobile node (200) by the MW Calculator (22) if the average value rate of change of RSS is below the user defined threshold;

e) averaging the upper and lower bound values based on a current value of Moving Weight to get a new value of Moving Weight; and f) forwarding the new value of Moving Weight to the CMP module (30) for the mobile node's (200) movement predicting process.

The method as claimed in claim 7, wherein predicting the movement of the mobile node (200) by the CMP module (30) includes the steps of:

a) collecting the RSS of the mobile node (200) for a period of time by the CMP RSS Collector (31);

b) calculating the rate movement of the mobile node (200) for a period of time by the Pattern Decision (32);

c) determining if the RSS values of the mobile node (200) is below a user defined threshold values by the MW Decision (33); and d) comparing the rate movement of the mobile node (200) with the values of the Moving Weight if the RSS values are below the defined threshold values to determine whether the mobile node (200) is leaving the current AC (400). The method for a handover in a wireless system as claimed in claim 7, wherein if neighbour APs (600a) are not under the ACCM Manager's (41a) control, the method includes the steps of:

a) broadcasting a message to determine the neighbour AC (500a) that manages the neighbour AP (600a) by the ACCM Manager (41a); b) replying to the broadcasted message if the neighbour APs (600a) are under its control by the neighbour AC (500a);

c) informing the ACCM Database (43a) to forward the context cache to the neighbour AC (500a) by the ACCM Manager (41a) upon receiving the reply; and

d) sending the context cache to the neighbour APs (600a) by the neighbour AC (500a).