GB2468469A

GB2468469A - Method of selecting an access point

Info

Publication number: GB2468469A
Application number: GB0811958A
Authority: GB
Inventors: Siok Kheng Tan; Zhong Fan
Original assignee: Toshiba Research Europe Ltd
Current assignee: Toshiba Europe Ltd
Priority date: 2008-06-30
Filing date: 2008-06-30
Publication date: 2010-09-08
Also published as: GB0811958D0

Abstract

A method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, comprises determining channel information, relating in particular to the loading, associated with each of the access points, generating at least one group of candidate access points arranged into priority levels based on the determined channel information, and selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.

Description

WIRELESS COMMUMCATION METHOD AND APPARATUS

Field of the Invention

The present invention relates to wireless communication. It is particularly, but not exclusively, concerned with a method and apparatus for selecting an access point in a

Background of the Invention

Wireless communication between electronic devices is becoming increasingly in demand, particularly due to the growth of multimedia communication services, such as video streaming, video conferencing, packet data transfer and so on. Accordingly, wireless networks are widely deployed to support these services. Generally, these networks are capable of supporting communications for multiple users by sharing the available network resources. One example of such network is a wireless local area network (WLAN).

A typical arrangement of a WLAN 10 is illustrated in Figure 1. Such a WLAN may include one or more access points (APs) 12, 14, 16 that serve one or more wireless devices (WD) 18. An AP (for example, 12) is typically a stand-alone device that is connected to an Ethernet switch (not shown) which can be in turn connected to a modem (not shown) to allow the wireless devices 18 to connect to the Internet. The AP 12 also bridges all data between the WDs 18a, 18b associated to it.

The wireless devices (WDs) described herein may be mobile terminals such as personal digital assistants (PDA5), notebook computers, or fixed terminals such as desktops and workstations that are equipped with a wireless network interface.

As shown in figure 1, two or more APs 12, 14, 16 may link together to form a larger network to allow the WDs 18 to roam from one WLAN lOa to another WLAN, for example 1 Ob or 1 Oc. Therefore, it is fundamental that a WD, having an established connection with an AP, is able to maintain the connection when the WD roams from one WLAN serviced by an AP to another WLAN serviced by another AP. It is even more important that the WI), having an established connection with an AP, maintains the connection at all time when moving within the same WLAN.

The signal strength (or more commonly referred to as RSSI -Received Signal Strength Indicator) of an AP serving a WD might degrade as the WI) moves beyond the coverage area of the AP (or when an interference occur). At this point, the WI) might be at risk of losing connectivity with the AP. In IEEE 802.11 WLAN systems, a WI) monitors the RSSI with respect to its associated AP and initiates a handoff only after services degrade below a predefined acceptable level.

Generally, the handoff process comprises the following steps: handoff trigger, channel scanning, access point selection, reauthentication, and reassociation.

Channel scanning provides neighbour APs information and facilitates handoff access point selection. Generally, there are two kinds of channel scanning methods namely, active and passive. During a passive channel scan, the WD passively listens for beacon messages sent out periodically by the APs. In active scanning, the WD actively probes the access points by sending a probe request to each of the APs within range, and receives response from these APs.

Conventional access point selection methods are generally based on RSSI information for selecting an access point to handoff. For example, in M Shin, A. Mishra, and W.A.

Arbaugh, "Context Caching using Neighbor Graphs for Fast Handoffs in Wireless Network, Proceedings of IEEE INFOCOM, March 2004, and S. Wa ha rta, K. Ritzenthaler and R. Boutaba, Selective Active Scanning for Fast Handoff in WLAN using Sensor Networks, Proceedings of the 6th IFIP/IEEE International Conference on Mobile and Wireless Communication Networks (MWCN 2004), Paris, France, October 2004, disclose methods of selecting a new access point for performing handoff based on RSSI information. Essentially, a wireless station selects to a new access point which has the highest RSSI value among other access points to perform the handoff operation.

However, using RSSI information for AP selection is insufficient as the WD may be connected to a new AP having the highest RSSI value but is also the busiest A? among other neighbouring APs. As a result, this can significantly affect the performance of applications running on the WD.

US200400398 17 describes an IEEE 802.11 conformant WLAN where a wireless station receives RSSI and channel information through beacon or probe response messages sent from the access points. The wireless station selects the access point during power-up or roam, based on the RSSI and channel loading information.

However, none of the prior art considers the average MAC delay experienced by the wireless device associated to the access point, which is also an important parameter for performing handoff in WLAN supporting QoS (Quality of Service) sensitive applications such as VoIP (Voice over IP).

Summary of the Invention

In a first aspect of the present invention, there is provided a method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the method comprising determining channel information associated with each of said access points, generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information, and selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.

Arranging the plurality of access points into a plurality of priority levels based on the channel information can allow the most suitable access point to be selected, and thereby improving the network efficiency of the wireless network.

The term "communication" as used herein preferably connotes transfer of data andlor information from the wireless device to the plurality of access points, or vice versa.

Such communication may for example comprise the wireless device performing channel scanning to monitor information associated with the channel of each of the access points. The term "connection" preferably connotes an ongoing communication link or data session between the wireless device and the selected access point.

The channel information may comprise an indication of congestion level associated with each of said access points, and/or an indication of traffic load at each of said access points. This can allow the traffic load and/or the congestion level to be taken into consideration when the wireless device selects a suitable access point to establish a communication link.

In one embodiment of the present invention, the group of candidate access points may be arranged such that the least congested access point is ranked as the highest priority.

In this embodiment, the wireless device will therefore be discouraged to select a congested access point to establish a communication link or data session.

In another embodiment of the present invention, the group of candidate access points may be arranged such that the access point having the least traffic load is ranked as the highest priority. In this embodiment, the wireless device will advantageously select the access point having the least traffic load to establish a communication link or data session.

The step of generating at least a group of candidate access points may include generating a group of candidate access points arranged by taking into consideration the congestion level and the traffic load at each of the access points. This can provide the wireless device with an additional choice of selecting the most suitable access point to establish the communication link. For example, the wireless device can select the access point which has a lighter traffic load and a lower congestion than any of the other access points.

The congestion level and the traffic level of each of the access points may be determined at the respective access points. Determining this information at the access points (as opposed to the wireless device) provides an advantage in that this information can be provided directly from the access points to the wireless device monitoring the channel of each of the access points, as opposed to the wireless device determining these information individually from each of the access points. It is noted this can allow efficient use of the available capacity of the network.

In one embodiment of the present invention, the congestion level may be a MAC (Medium Access Control) frame delay of a data packet according to the IEEE 802.11 WLAN standard. It will be appreciated that the MAC delay represents the time period when a data packet is sent from the wireless device and when an acknowledgement message is received at that wireless device.

By using an exponential weighted moving average (EWMA) method, the MAC delay may be obtained by D(j)=aD(j-1)+(1-a)Y(j) where D(j) is the EWMA at time window j, D(j -1) is the EWMA at time window j -I,Y(j) is the average MAC delay measurement collected at time window j, and a is a smoothing factor between 0 to 1.

The traffic level may be determined by the following expression: L(j) aL(j-I)+(1-a)X(j) where L(j) is the exponential weighted moving average (EWMA) at the time window j, L(j -1) is the average load measurement collected at time window j, and a is a smoothing factor between 0 to 1 The step of selecting the candidate access point may include any one of the following: (i) selecting the access point based on the congestion level; (ii) selecting the access point based on the traffic load; (iii) selecting the access point based on a combination of congestion level and traffic load.

Thus this can allow the most appropriate access point to be selected for the wireless device to establish a connection. For example, the wireless device can be connected to an access point with the least congestion and the lowest traffic load in the wireless network.

In a second aspect of the present invention, there is provided a method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the method comprising determining channel information associated with each of said access points, selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point, and wherein said channel infonnation include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.

In a third aspect of the present invention, there is provided an apparatus for selecting an access point in wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points, means for generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information, and means for selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.

In a fourth aspect of the present invention, there is provided a wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in conimunication with said plurality of access points, the wireless device being operable to determine channel information associated with each of the access points, to generate a group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information, and to select a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.

In a fifth aspect of the present invention, there is provided an apparatus for selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points, means for selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point, and wherein said channel information include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.

In the sixth aspect of the present invention, there is provided a wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the wireless device being operable to determine channel infonnation associated with each of said access points, to select one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point, and wherein said channel information include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.

Aspects of the invention may comprise a computer program product comprising computer executable instructions operable to cause a computer to become configured to perform a method in accordance with any of the above identified aspects of the invention. The computer program product can be in the form of an optical disc or other computer readable storage medium, a mass storage device such as a flash memory, or a read only memory device such as ROM. The method may be embodied in an application specific device such as an ASIC, or in a suitably configured device such as a DSP or an FPGA. A computer program product could, alternatively, be in the form of a signal, such as a wireless signal or a physical network signal.

Brief description of the drawings

Embodiments of the present invention will now be described with reference to the accompanying drawings, wherein: Figure 1 illustrates an exemplary prior art WLAN arrangement; Figure 2 is a schematic diagram of an example wireless device; Figure 3 is a flow diagram illustrating a process of triggering a handoff at a wireless device; Figure 4 is a flow diagram illustrating an access point selection process in accordance with a first embodiment of the invention; Figure 5 is a flow diagram illustrating an access point selection process in accordance with a second embodiment of the invention; Figure 6 is a flow diagram illustrating an access point selection process in accordance with a third embodiment of the invention; Figure 7 is a flow diagram illustrating an access point selection process in accordance with a fourth embodiment of the invention; and Figure 8 is a WLAN arrangement illustrating selection of an access point in accordance with the embodiments of the invention;

Detailed Description

Specific embodiments of the present invention will be described in further detail on the basis of the attached diagrams. It will be appreciated that this is by way of example only, and should not be viewed as presenting any limitation on the scope of protection sought.

Figure 1 has been described above in relation to the prior art example. For consistency, the invention will now be described by way of specific embodiment in relation to the arrangement illustrated in figure 1.

In figure 1, three APs 12, 14, 16 are illustrated. Each of these APs connects WDs 18 together to form a WLAN (lOa, lOb, or lOc). Typically the coverage ranges of an AP ranges within a radius of 100 metres. The APs can also be link together to form a larger wireless network such that the WDs 18 can roam from one WLAN to another WLAN.

Figure 2 illustrates schematically a wireless device (WD) 18 providing an example of background to the invention. The WD 18 comprises a processor 20 operable to execute machine code instructions stored in a working memory 24 andlor retrievable from a mass storage device 26. By means of a general-purpose bus 28, user operable input devices 30 are in communication with the processor 20. The user operable input devices 30 comprise, in this example, a keyboard and a touchpad, but could include a mouse or other pointing device, a contact sensitive surface on a display unit of the device, a writing tablet, speech recognition means, haptic input means, or any other means by which a user input action can be interpreted and converted into data signals.

Audio/video output devices 32 are further connected to the general-purpose bus 28, for the output of information to a user. Audio/video output devices 32 include a visual display unit, and a speaker, but can also include any other device capable of presenting information to a user.

A communications unit 36 is connected to the general-purpose bus 28, and further connected to an antenna 38. By means of the communications unit 36 and the antenna 38, the WD 18 is capable of establishing wireless communication with another device (for example, an AP). The communications unit 36 is operable to convert data passed thereto on the bus 28 to an RF signal carrier in accordance with a communications protocol previously established for use by a system in which the WD 18 is appropriate for use.

In the WD 18 of figure 2, the working memory 24 stores user applications 34 which, when executed by the processor 20, cause the establishment of a user interface to enable communication of data to and from a user. The applications 34 thus establish general purpose or specific computer implemented utilities and facilities that might habitually be used by a user.

The example commences in a situation whereby the WD monitors the current RSSI of the AP with which the WD is currently connected, and initiates a handoff when the current RSSI value degrade below a predefined acceptable level. This process is illustrated in figure 3.

Referring to figure 4, the WD begins a channel scanning process to obtain APs information from each of the respective APs that are within the vicinity of the WD. It will be appreciated that any channel scanning (active or passive) method can be applied in order to obtain the APs information associated with the respective AP. The AP information can, for example, include an indication of congestion level, an indication of traffic load, and RSSI value of the AP.

It will be appreciated that the congestion level and traffic load of an AP can be determined using a number of existing methods.

One example of determining the indication of traffic load of an AP is by determining the traffic load in terms of data (byte/packet) over a duration (such as the beacon interval, T). At the end of T, the AP calculates the existing average traffic load using the following exponential weighted moving average (EWMA) equation L(j) aL(j -1)+ (1 -ct)X(j) where L(j) is the exponential weighted moving average (EWMA) at the time window j, L(j -1) is the EWMA at time window j -1, X(j) is the average load measurement collected at time window j, and a is a smoothing factor between 0 to 1.

One advantage of the EWMA filter is that it gives importance of the current measurement while not discarding the older measurement, thereby allowing the traffic load calculation to be more responsive to recent changes.

It will be appreciated that MAC delay represents the time it takes to send a frame between an AP and a WD, which can be determined by observing the actual time for the channel to transmit the data frame, and is expressed as: DI =t t where tRlS the time an acknowledgement (ACK) message is received at the WD and t is the time the data frame is sent from the WD.

Similarly, applying the EWMA equation, the MAC delay is obtained by D(j)=aD(j-l)+(1-a)Y(j) where D(j) is the EWMA at time window j, D(j -1) is the EWMA at time window j -1, Y(j) is the average MAC delay measurement collected at time window j, a is a smoothing factor between 0 to 1.

With these information, the WD can commence a selection process to select the best AP to handoff.

The selection process according to a first embodiment of the invention will be discussed with reference to the flow chart of figure 4. In figure 4, steps 52 to 78 represent a loop in which the WD starts the selection process by considering all the APs (candidate APs) within its vicinity through channel scanning. For each candidate AP, the associated "Channel_flag" value is set to zero (step 54).

In step 56, the RSSI value of the candidate AP (RSSI_candidate_AP) is compared with the RSSI value of the current AP channel (RSSI current) with which the WD is associated. The AP will only be prioritised based on its MAC delay and traffic load only if the RSSI_candidate_AP value is higher than the RSSI_current. However, if the RSSI_candidateAp is lower than the RSSI_current, the candidate channel RSSI_candidate_AP will be compared with the RSSI_current_AP -RSSI_threshold (RSSI threshold value of the current AP channel) in step 58. If RSSI_candidate_AP is less than the RSSI_current for more than the predefined RSSI_threshold, the candidate channel will not be considered and the selection process will proceed to consider the next AP in its vicinity. If the RSSI_candidate_AP is lower than the RSSI_current for less than the predefined RSSI_threshold, the respective "Channel_flag" value will be set to one (step 60). Consequently, the AP will be considered for prioritising based on its MAC delay and traffic load.

It is noted that the RSSI comparison (from step 56 to step 60) is performed between two different APs (that is the current AP and a candidate AP), while the RSSJ comparison for handoff triggering (in figure 3) is related to a comparison between the old RSSI value and the new RSSI value of the same AP (the current AP).

In step 62, the MAC delay of the candidate AP (MAC_Delay_candidate_AP) is compared with a predetermined MAC delay threshold (MAC_Delay_threshold) value.

If the MAC_Delay_candidate_AP is higher than the MAC_Delay_threshold, the candidate AP will not be considered and the selection process proceeds to consider the next AP. It is noted that step 62 is used to ensure that a channel which has a MAC delay larger than a predefined value is not considered for supporting some applications, for example VoIP traffic (which tolerates up to 5Oms latency).

If the MAC Delay candidate AP is lower than the MAC_Delay_threshold, the selection process will proceed to compare the MAC_Delay_candidate_AP with the MAC delay (MAC_Delay_current) of the AP with which the WD is currently associated (step 64). If the MAC_Delay_candidate_AP is higher than MAC_Delay_current, the traffic load of the candidate AP (Traffic_Load_candidate) will be compared with the traffic load of the AP (Traffic_Load_current) with which the WI) is currently associated (steps 66 and 68). If the Traffic_Load_candidate value is higher than the Traffic_Load_current value and the Channel_flag is zero, the candidate AP will be categorised as level 1 (step 72). Otherwise (if the Channel_flag is one) the AP will not be considered, as this will be a situation when all the three parameters (RSSI, MAC delay and traffic load) of the candidate AP are worse than the current AP. However, if the Traffic_Load_candidate value is lower than the Traffic_Load_current value, the AP will be categorised as level 2 (step 74).

Similarly, if the MAC Delay candidate AP is lower than MAC_Delay_current, the Traffic_Load_candidate will be compared with the Traffic_Load_current. However, if Traffic_Load_candidate is higher than Traffic_Load_current, the candidate AP will be categorised as level 3 (step 76). Otherwise, it will be categorised as level 4 (step 78).

Following the process described above, the next neighbouring AP will be considered (step 52). If there is no more candidate access point to be considered, the selection process proceeds to step 80 to select the best access point by considering the AP from the highest to the lowest level. In this example, level 4 is the highest level and level 1 is the lowest level. If there is more than one AP available in the highest priority level, the AP with a higher RSSI will be selected.

The selection process according to a second embodiment of the invention will be discussed with reference to the flow chart of figure 5.

Essentially, the selection process illustrated in figure 5 is similar to that described in figure 4 above, except that the selection process of figure 5 does not take into consideration the traffic load of the AP (it is noted that steps 66, 68, 74 and 78 of figure 4 are eliminated in figure 5). In this case, the selection process considers only the RSSI value and the MAC delay of each of the candidate APs.

The selection process according to a third embodiment of the invention will be discussed with reference to the flow chart of figure 6.

The handoff trigger and the steps (steps 120 to 130) involving RSSI comparison of this embodiment are similar to the selection process described above with reference to the flow chart of figure 4. Referring to figure 6, in step 132 the traffic load of the candidate AP (Traffic_Load_candidate) is compared with the traffic load of the AP (Traffic_Load_current) with which the WD is currently associated. If the Traffic_Load_candidate value is higher than the Traffic_Load_current, the MAC delay of the candidate AP (MAC_Delay_candidate_AP) will be compared with the MAC delay of the AP (IVIAC_Delay_current) with which the WD is associated (step 134). If the value of MAC_Delay_candidate_AP is higher than MAC_Delay_current and the Channel flag of the candidate channel is zero, the candidate AP will be categorised as level 1 (step 140). Otherwise (if the Channel_flag is one) the AP will not be considered, as this will be a situation when all the three parameters (RSSI, MAC delay and traffic load) of the candidate AP are worse than the current AP. However, if the MAC_Delay_candidate_A? value is lower than the MAC_Delay_current value, the access point will be categorised as level 2 (step 142).

In contrast, if the Traffic_Load_candidate is lower than the Traffic_Load_current, the MAC_Delay_candidate_A? will be compared with the MAC_Delay_current. If MAC_Delay_candidate_A? is higher than MAC_Delay_current, the candidate access point will be categorised as level 3 (step 144). Otherwise, it will be categonsed as level 4 (step 146).

Similarly, following the process described above, the next neighbouring access point will be considered (step 122). If there is no more candidate access point to be considered, the selection process proceeds to step 148 to select the best access point by considering the access point from the highest to the lowest level. In this example, level 4 is the highest level and level 1 is the lowest level. If there is more than one access point available in the highest priority level, the access point with a higher RSSI will be selected.

The selection process illustrated in figure 7 is similar to that described in figure 6 above, except that the selection process of figure 7 does not take into consideration the MAC delay of the A? (essentially, steps 134, 136, 142 and 146 of figure 6 are eliminated in this figure). In this case, the selection process considers only the RSSI value and the traffic load of each of the candidate APs.

An example of selecting an AP in a WLAN in accordance with the above described methods will now be described with reference to figure 8.

Figure 8 shows a wireless device (herein referred to as WD1) 180 moving away from its current AP (AP3) 182. In this situation, handoff will be triggered by the WI) as the RSSI value degrades below a predefined threshold. Under conventional access point selection method, AP2 184 will be the preferred access point to handoff as it has the highest RSSI compared to other available access points within the vicinity of WD1.

However, as shown in figure 8, AP2 may not be the best access point to handoff to as it has the highest traffic load arid the highest MAC delay.

In contrast, under the proposed selection method described above, the WD1 will consider APi 186 to perform handoff as APi 186 has medium RSSI value, low traffic load and low MAC delay. By applying the selection method of the invention, the most suitable access point can be selected, and therefore the network efficiency of the wireless network can be significantly improved.

It will be understood that the invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

CLAIMS: A method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the method comprising determining channel information associated with each of said access points; generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel infonnation; and selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.
2. A method according to claim 1 wherein the channel information comprises an indication of congestion level associated with each of said access points, andlor an indication of traffic load at each of said access points.
3. A method according to claim 2 wherein the group of candidate access points is arranged such that the least congested access point is ranked as the highest priority.
4. A method according to claim 2 wherein the group of candidate access points is arranged such that the access point having the least traffic load is ranked as the highest priority.
5. A method according to any one of claims 2 to 4 wherein the step of generating at least a group of candidate access points includes generating a group of candidate access points arranged by taking into consideration the congestion level and the traffic load at each of the access points.
6. A method according to any one of claims 2 to 5 wherein the congestion level and the traffic level of each of the access points is determined at the respective access points.
7. A method according to any one of the preceding claims wherein the step of selecting the candidate access point includes any one of the following: (i) selecting the access point based on the congestion level; (ii) selecting the access point based on the traffic load; and (iii) selecting the access point based on a combination of congestion level and traffic load.
8. A method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the method comprising determining channel information associated with each of said access points; selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point; and wherein said channel information include an indication of congestion level at each of said access points, and/or an indication of traffic load at each of said access points.
9, An apparatus for selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points; means for generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information; and means for selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.
10. An apparatus according to claim 9 wherein means for determining the channel information is operable to determine an indication of congestion level associated with each of said access points, and/or an indication of traffic load at each of said access points.
11. An apparatus according to claim 10 further comprises means for arranging the group of candidate access points such that the least congested access point is ranked as the highest priority.
12. An apparatus according to claim 10 further comprises means for arranging the group of candidate access points such that the access point having the least traffic load is ranked as the highest priority.
13. An apparatus according to any one of claims 10 to 12 wherein the means for generating at least a group of candidate access points is further operable to generate a group of candidate access points arranged by taking into consideration the congestion level and the traffic load at each of the access points.
14. An apparatus according to any one of claims 10 to 13 wherein the congestion level and the traffic level of each of the access points is determined at the respective access points.
15. A wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, wherein the wireless device is operable to determine channel information associated with each of the access points, to generate a group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information, and to select a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.
16. An apparatus for selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points; means for selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point; and wherein said channel information include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.
17. A wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, wherein the wireless device is operable to determine channel information associated with each of said access points, to select one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point, and wherein said channel information include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.
18. A storage medium storing computer executable instructions which, when executed on general purpose computer controlled communications apparatus, cause the apparatus to become configured to perform the method of any of claims 1 to 8.
19. A signal carrying computer receivable information, the information defining computer executable instructions which, when executed on general purpose computer controlled communications apparatus, cause the apparatus to become configured to perform the method of any of claims ito 8.Amendments to the Ciams have been flied as follows: CLAIMS: 1. A method of selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the method comprising determining channel information associated with each of said access points, the channel information comprising an indication of congestion level associated with each of the access points and wherein the congestion level is a MAC (medium access control) frame delay of data packets according to the IEEE 802.11 WLAN Standard; generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels * a.. based on said determined channel information; and * : * selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish * : : :* a connection with the selected candidate access point.2. A method according to claim 1 wherein the channel information further : comprises an indication..of traffic load at each of said access points.S3. A method according to claim 2 wherein the group of candidate access points is arranged such that the least congested access point is ranked as the highest priority.4. A method according to claim 2 wherein the group of candidate access points is arranged such that the access point having the least traffic load is ranked as the highest priority.5. A method according to any one of claims 2 to 4 wherein the step of generating at least a group of candidate access points includes generating a group of candidate access points arranged by taking into consideration the congestion level and the traffic load at each of the access points.1 323029-2-dchew 6. A method according to any one of claims 2 to 5 wherein the congestion level and the traffic level of each of the access points is determined at the respective access points.7. A method according to any one of the preceding claims wherein the step of selecting the candidate access point includes any one of the following: (i) selecting the access point based on the congestion level; (ii) selecting the access point based on the traffic load; and (iii) selecting the access point based on a combination of congestion level and traffic load.** * 8. A method of selecting an access point in a wireless network having a plurality of * : * * access points and at least one wireless device being in communication with said plurality of access points, the method comprising *: * determJx�ig channel information associated with each of said access points; selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection *..S** * with the selected access point; and wherein said channel information include an indication of congestion level at each of said access points, andlor an indication of traffic load at each of said access points.9. An apparatus for selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points, the channel information comprising an indication of congestion level associated with each of the access points and wherein the congestion level is a MAC (medium access control) frame delay of data packets according to the IEEE 802.11 WLAN Standard; 1 323029-2-d chew means for generating at least one group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information; and means for selecting a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.10. An apparatus according to claim 9 wherein means for determining the channel information is operable to determine an indication of traffic load at each of said access points.11. An apparatus according to claim 10 further comprises means for arranging the group of candidate access points such that the least congested access point is ranked as the highest priority.S* 12. An apparatus according to claim 10 further comprises means for arranging the *: ::* group of candidate access points such that the access point having the least traffic load is ranked as the highest priority. * I * S S* 13. An apparatus according to any one of claims 10 to 12 wherein the means for *S.*.* * generating at least a group of candidate access points is further operable to generate a group of candidate access points arranged by taking into consideration the congestion level and the traffic load at each of the access points.14. An apparatus according to any one of claims 10 to 13 wherein the congestion level and the traffic level of each of the access points is determined at the respective access points.15. A wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, wherein the wireless device is operable I 323029-2-dchew to determine channel information associated with each of the access points, to generate a group of candidate access points consisting of said plurality of access points being arranged into a plurality of priority levels based on said determined channel information, and to select a candidate access point based on the priority level of said group of candidate access points, so as to allow said wireless device to establish a connection with the selected candidate access point.16. An apparatus for selecting an access point in a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, the apparatus comprising means for determining channel information associated with each of said access points; S...*:" means for selecting one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point; and * wherein said channel information include an indication of congestion *:*. level at each of said access points, and/or an indication of traffic load at each of said access pomts. S *17. A wireless communications system comprising a wireless network having a plurality of access points and at least one wireless device being in communication with said plurality of access points, wherein the wireless device is operable to determine channel information associated with each of said access points, to select one of said plurality of access points based on the determined channel information, so as to allow said wireless device to establish a connection with the selected access point, and wherein said channel information include an indication of congestion level at each of said access points, and/or an indication of traffic load at each of said access points.1 323029-2-dchew 18. A storage medium storing computer executable instructions which, when executed on general purpose computer controlled communications apparatus, cause the apparatus to become configured to perform the method of any of claims 1 to 8.19. A signal carrying computer receivable information, the information defining computer executable instructions which, when executed on general purpose computer controlled communications apparatus, cause the apparatus to become configured to perform the method of any of claims 1 to 8. * S ****SS..... * S * S. * S * * S. * . * * .*S I *1 323029-2-dchew