Patent Application
20050138178
Embodiments of the invention generally relate to the field of wireless communications. More particularly, one or more embodiments of the invention relate to a wireless mobility manager and its method of operation.
Wireless technology provides a mechanism for either replacing or extending traditional wired networks including, but not limited to, local area networks (LANS), personal area networks (PAN) and metropolitan area networks (MAN). Using radio frequency (RF) or non-RF technology, wireless networks transmit and receive data over the air, through walls, ceilings and even cement structures without wired cabling. For example, a wireless LAN (WLAN) is a flexible data communication system that provides all the features and benefits of traditional LAN technology, such as Ethernet and Token Ring, but without the limitations of being tethered together by a cable. This provides increased freedom and flexibility.
In other words, a WLAN is a network in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection according to a wireless protocol. Wireless protocols include, but are not limited to IEEE 802.11 (e.g., IEEE 802.11a, 802.11b, 802.11g), HiperLAN (e.g., HiperLAN1, HiperLAN2, etc.), or any other wireless communication protocol. These wireless protocols are designed to provide high bandwidth allocation at a relatively low cost, without the need for substantial rewiring of various structures.
Mobility is a major motivation for deploying a wireless network. This mobility allows devices to move while connected to the network and transit frames while in motion. However, the mobility provided by wireless networks is restricted by several constraints. For example, wireless networks are implemented at the link layer, and therefore, are limited to providing link layer mobility. By way of contrast, the Internet protocol (IP) affords the network designer no such luxury. Although wireless devices can freely move within a network, IP, as it is currently deployed, provides no way to move across subnet boundaries.
In other words, one current requirement for mobility of a wireless device is that the IP address of the wireless device can not change when connecting to any of the access points. Accordingly, all wireless devices must remain on the same subnet. As long as the wireless device stays on the same IP subnet, it does not need to re-initialize its network stack and it can keep its transmission control protocol (TCP) connections open. However, if the wireless device leaves the subnet, the device is required to get a new IP address and re-establish any open connection.
Accordingly, wireless device mobility is limited to various access points within a single subnet. Furthermore, as the wireless device moves between the various access points of the single IP subnet, the wireless device must perform an authentication and association procedure with a new subnet access point. Therefore, as the wireless device roams within the subnet, the user must know and manually enter a Wired Equivalence Privacy (WEP) key in order to switch between access points of the subnet to maintain communication with the subnet. This increases the amount of user activity required to roam within a subnet.
The various embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompany drawings, and in which:
Embodiments of the invention generally relate to a wireless mobility manager and its associated operation as described herein. In one embodiment of the invention, a wireless mobility manager monitors the signal quality of a current wireless connection to a wireless access point. Without user intervention, a scan may be conducted to identify one or more wireless access points within a current communication range when the signal quality of the current wireless connection falls below a SCAN THRESHOLD. The signal quality may be based on signal strength, signal-to-noise ratio (SNR), error rate, connection count or the like. The SCAN THRESHOLD may be either a preset value or a programmable value that is set by the user.
Once scanning is complete, the wireless mobility manager determines whether the signal quality of the current wireless connection falls below a SWITCH THRESHOLD, either a preset value or a programmable value that is set by the user and normally less than the SCAN THRESHOLD. If so, the wireless mobility manager allows the wireless station to establish a new wireless connection with another wireless access point selected from the one or more identified access points. This “handoff” is conducted without user intervention as well.
According to another embodiment of the invention, the wireless station, having a wireless connection with an access point of a first network, roams into communication range of a second network. Once the wireless station roams into communication range of the second network, the wireless station establishes a wireless connection with a selected access point of the second network. In one embodiment of the invention, the wireless mobility manager of the wireless station determines a signal strength of one or more access points of the second network. In addition, the wireless station may determine various quality of service (QoS) characteristics of the identified access points in order to select an access point based on signal strength and/or QoS characteristics. Hence, the user of the wireless station experiences a quality of service from the selected access point, which is roughly equivalent to the level of service provided by a current wireless connection while experiencing a continuous wireless network connection without requiring user intervention.
In the following description, certain terminology is used to describe features of the invention. For example, the term “group” represents one or more. The term “logic” is representative of hardware and/or software configured to perform one or more functions. For instance, examples of “hardware” include, but are not limited or restricted to, an integrated circuit, a finite state machine or even combinatorial logic. The integrated circuit may take the form of a processor such as a microprocessor, application specific integrated circuit, a digital signal processor, a micro-controller, or the like.
An example of “software” includes executable code in the form of an application, an applet, a routine or even a series of instructions. The software may be stored in any type of machine readable medium such as a programmable electronic circuit, a semiconductor memory device inclusive of volatile memory (e.g., random access memory, etc.) and/or non-volatile memory (e.g., any type of read-only memory “ROM,” flash memory), a floppy diskette, an optical disk (e.g., compact disk or digital video disk “DVD”), a hard drive disk, tape, or the like.
The term “wireless station” or “station” is used to refer to a portable device adapted to receive and/or transmit wireless data. Examples of a wireless station include, but are not limited to a computer, a personal digital assistant (PDA), a wireless appliance, or any other portable device configured to communicate via a wireless communications medium such as, for example, radio frequency (RF) waves.
Furthermore, as described herein, the term “access point” or “AP” is an electronic device that provides a connection between one or more wireless stations and a network such as the wired interconnect. According to one embodiment, the connection is bi-directional although this bi-directional connection is not a requirement.
I. System Architecture
A virtual private network (VPN) server 160 may be included in the mobility communications system 100 to provide security and encryption/decryption capabilities to the system 100 utilizing, for example, the IP Security (IPSec) protocol. A remote authentication dial-in user service (RADIUS) server 190 may be included in mobility communications system 100 to provide authentication and accounting of users of the system 100. Other authentication protocols and server systems may be implemented as well, and integration with other authentication protocols, such as the Diameter protocol, for example, may be implemented. Furthermore, a domain server 180 may be included in mobility communications system 100 to facilitate access to and from the Internet 102 via router 106.
Herein, as an example, one or more wireless local area networks (WLAN) 200 are coupled LAN backbone 110. Such coupling may be accomplished by multiple routers or a single router 170 as shown. In one embodiment of the invention, each WLAN 200 comprises a switch 210 that is coupled to a node server 220. Although generally referenced as WLAN 200, switch 210 and node server 220, each of these elements are separately and specifically represented as WLAN 200-1 . . . WLAN 200-N (N≧1), switch 210-1 . . . switch 210-N, and node server 220-1 . . . node server 220-N, respectively. Each WLAN 200 also comprises one or more access points (AP) 230 (e.g., AP 230-1, . . . , AP 230-M, where M≧1).
More specifically, WLAN 200-1 is being accessed by wireless stations 300-1 and 300-2. In this illustrated embodiment, for example, wireless station 300-1 accesses WLAN 200-1 via AP 230-1. Likewise, wireless station 300-2 accesses WLAN 200-1 via AP 230-2. Herein, both APs 230-1 and 230-2 are represented as being part of the same subnet. A different WLAN, namely WLAN 200-N, provides a similar configuration to WLAN 200-1.
Prior to communicating data, wireless stations 300 establish an association with their corresponding APs 230. After an association is established, wireless stations 300 and APs 230 exchange data. In the infrastructure mode, the wireless stations 300 associate with an access point. The association process is a two step process involving three states: (1) “unauthenticated and unassociated”; (2) “authenticated and unassociated”; and (3) “authenticated and associated”. To transition between the states, the communicating parties exchange messages called management frames. In operation, all APs transmit a beacon management frame at a fixed interval.
As an example, to associate with an AP 230-2 and join a wireless network, a wireless station 300-2 listens for beacons to identify APs within its communication range. After identifying AP 230-2, the wireless station 300-2 and the AP 230-2 may perform a mutual authentication by exchanging several management frames as part of the process. After successful authentication, the wireless station 300-2 moves into the second state, authenticated and unassociated. Moving from the second state to the third and final state, authenticated and associated, involves the wireless station 300-2 sending an association request frame and the AP responding with an association response frame.
In one embodiment of the invention, mobility communications system 100 may be configured as an enterprise network with various APs throughout the floors of the building or different buildings and surroundings forming a corporate campus. APs 230 communicate with wireless stations 300 via radio frequency waves, such as, for example, according to an IEEE 802.11 protocol, a HiperLAN protocol or the like. Unfortunately, as wireless station 300-2 roams, association with a detected AP of a WLAN or subnet may be prohibited without wireless station 300-2 having some form of authentication information to enable association with a selected AP. In one embodiment, a wireless station 300-2 may roam from WLAN 200-1 to WLAN 200-N, while maintaining a continuous wireless connection to mobility communications network 100 without requiring any user intervention.
In one embodiment of the invention, a continuous wireless connection is enabled by downloading an AP list to which a user of wireless station 300-2 has user access privileges. Accordingly, as a user roams throughout mobility communications network 100, wireless station 300-2 maintains a connection with network 100 without requiring user intervention. In one embodiment of the invention, mobile communications (MCS) server 120 is configured to provide a wireless station, upon initial login, with an AP list that contains each AP to which a user of the wireless station has access privileges.
According to conventional techniques, wireless AP switching, which may be referred to herein as “AP hand off” is generally not performed by a wireless station until a signal level of the station is unusable. Furthermore, conventional techniques prohibit a wireless station from roaming from a first subnet, such as WLAN 200-1, to a second subnet, such as WLAN 200-N, since an Internet protocol (IP) address assigned to the wireless station will not allow the wireless station to function within the second subnet without requesting assignment of a new IP address. Furthermore, wireless AP switching does not generally enable voice communication since bandwidth pre-allocation for quality of service (QoS) or load balancing is not provided via conventional techniques.
Accordingly, in one embodiment of the invention, wireless stations 300 are configured to include a wireless mobility manager (WMM), which functions in conjunction with MCS server 120, as well as QoS/load balance server 130, to enable wireless AP scan and subsequent AP switching. This provides the user with a continuous wireless connection to mobility communications network 100 without user intervention.
Moreover, a dynamic host configuration protocol (DHCP) and/or a dynamic rapid configuration protocol (DRCP) server 150, also connected LAN backbone 110, are configured to assign IP addresses to the nodes of mobility communications network 100, as well as an IP address for subnet roaming. Accordingly, in one embodiment, wireless stations 300 are configured, as is depicted with reference to
Referring now to
As illustrated, wireless station 300 may download an AP list 450, which includes one or more APs (and perhaps stations) of, for example, each node or subnet of mobility communications system 100 (
In one embodiment of the invention, AP list 450 may comprise, for example, a data structure, as depicted with reference to Table 1. This differs from conventional wireless AP switching which requires user intervention to provide a name (SSID) and to manually enter a wired equivalence privacy (WEP) key before the user's wireless station associates with a selected AP. Conversely, AP list 450 provides the necessary information to wireless station 300 to enable automatic association with any member APs, via communications interface 320, without requiring any user intervention.
In one embodiment of the invention, the wireless station switching described herein is supported by WMM logic 400. As illustrated, AP handoff logic 410, in one embodiment, includes or operates in conjunction with AP scan logic 420. AP scan logic 420 uses a user selected SCAN THRESHOLD, which is compared to, for example, a signal strength of a current wireless connection to an AP by wireless station 300. In one embodiment, when the signal strength of the current wireless connection falls below the SCAN THRESHOLD, AP scan logic 420 will utilize AP list 450 to identify one or more APs within the communication range of the station, for example, as illustrated with reference to
In one embodiment, scan logic 420 uses a wireless media access control (MAC) address to identify AP membership regarding one or more identified APs. Accordingly, WMM logic 400 operation is possible even if the APs do not broadcast their service set identity (SSID) identifier for security reasons, and it is also possible to have multiple APs with the same SSID operational as well. Therefore, a correct wireless MAC address and SSID for each AP is entered into an AP database (not shown). Usually, the MAC address is found on a label on the back of the wireless AP. Accordingly, AP list 450 comprises at least an SSID and a MAC address for each listed AP.
Once AP scan logic 420 identifies one or more available APs, AP switch logic 430 further monitors the current wireless connection of the wireless station to determine whether a signal strength of the current wireless connection falls below a user selected SWITCH THRESHOLD. When such is the case, AP switch logic 430 selects one of the identified APs and performs an authentication and association procedure with the selected AP. In one embodiment, the SCAN THRESHOLD, as well as the SWITCH THRESHOLD, are provided by a user via user interface (UI) 360, which is further illustrated with reference to
As illustrated in
Furthermore, screen 460 comprises a field 466 that indicates the number of currently available APs within the AP list. Also, screen 460 further comprises a user selection button 468. According to one embodiment, when selected, the user selection button 468 automatically refresh a current AP list from MCS server 120 of
Referring back to
In a further embodiment, wireless station 300-2 may request, for example, from node server 220-1 and/or QoS/load balance server 130, pre-allocation of a certain bandwidth from an available AP. QoS/load balance server 130 attempts to pre-allocate the selected bandwidth from an AP. Once server 130 assigns an AP with the requested bandwidth, QoS/load balancing server 130 provides AP handoff logic 410 with the selected AP, in addition to any connection information required to perform association and authentication with the selected AP.
Accordingly, referring to
For example, as illustrated, wireless station 300 will detect AP2230-2, as well as AP3230-3. As illustrated, wireless station 300 is currently connected to AP1230-1. Furthermore, AP2230-2 is a member of the same subnet as AP1. Conversely, AP3230-3 is a member of second subnet 200-2. As such, in order to perform association and authentication with AP3230-3, wireless station may query AP list 450. However, in order to continue uninterrupted data communications, wireless station 300 is required to use a new IP address for communications within subnet 200-2.
According to one embodiment of the invention, MCS server 120 pre-requests a temporary IP address for wireless station 300, which is included within AP list 450 corresponding to AP3230-3 and AP4230-M. In an alternative embodiment, wireless station 300 detects that AP3230-3 is on a different subnet (“new subnet detection”) and requests an IP address to enable communication within the second subnet 200-2. In one embodiment, new subnet detection is performed by evaluating the following conditional expression:
(mask & AP IP)=? (mask & current IP) (1)
In one embodiment, if evaluation of the conditional expression (1) returns a true value, the wireless station 300 and AP are on the same subnet. Otherwise, the AP and wireless station 300 are on different subnets. Hence, wireless station 300 requires a new IP address to communicate within the subnet of the AP. Accordingly, in one embodiment, wireless station 300 either utilizes a pre-allocated IP address from MCS server 120 or requests an IP address from, for example, DHCP/DRCP server 150, for communication within subnet 200-2.
In one embodiment, wireless station 300 utilizes session initiation protocol mobile (SIP-M) for voice communications (packet based) and utilize the mobile Internet protocol (mobile IP) for data communications. Representatively, mobile IP permits a wireless station to move from one network link (or subnet) to another without interrupting data communications. Accordingly, as illustrated with reference to
II. Operations
In one embodiment, in order to reduce the performance impact of the wireless mobility manager (WMM) functionality described herein, the wireless station may discontinue scanning if the current signal strength rises above the user selected SCAN THRESHOLD, which are provided by adjustment via the user interface.
At process block 540, the wireless station determines whether the current signal strength of the current wireless station connection falls below a user selected SWITCH THRESHOLD. In the embodiments illustrated, the SWITCH THRESHOLD represents a weaker or less powerfull signal than the user selected SCAN THRESHOLD. In one embodiment, the SWITCH THRESHOLD is selected to avoid interruption of wireless communication, but below which such communication may be interrupted. Accordingly, at process block 550, the wireless station establishes a wireless connection with the selected AP from the one or more identified APs.
In the embodiment described in
In another embodiment of the invention, the selection of a new AP may be prompted and/or based on a signal-to-noise ratio, which is determined for each identified AP. As such, for voice, as well as certain data communications such as streaming media for example, identified APs may exhibit sufficient signal strength while exhibiting unacceptable signal-to-noise ratios.
Likewise, the selection of a new AP may be prompted and/or based on a bit error rate of each identified AP. This measurement would likely be used for wireless stations supporting voice communications, which generally should not be perform by an AP which exhibits a significant bit error rate.
In yet another embodiment of the invention, the selection of a new AP may be prompted and/or based on a relative signal strength (RSS) slope computation. The RSS slope computation, which measures the rate of degradation of signal strength between the wireless station and the current AP, is computed as the ratio between the previously measured signal strength and the current measured signal strength.
For instance, as one example, when the measured signal strength of the current wireless connection falls below the SCAN THRESHOLD and RSS slope computation is less than a predetermined value, which may be preset or set by the user, the wireless mobility manager prompts the wireless station to scan and identify APs in its communication range. This avoids repeatedly scan operations when the signal strength oscillates around the SCAN THRESHOLD.
Alternatively, as a second example, when the RSS slope computation is less than the predetermined value, the wireless mobility manager prompts the wireless station to scan and identify APs in its communication range. This avoids loss of a connection where the signal strength quickly degrades.
In an alternative embodiment, MCS server notifies a node of the second network or subnet of the assigned IP address to enable data communication with the second network. Alternatively, DHCP/DRCP server notifies the second network of an IP address assigned to the wireless station. In one embodiment, the IP address is issued for limited duration of time to avoid excessive issuing of new IP address to enable interdomain roaming. Accordingly, in one embodiment, a wireless station including WMM logic described herein provides a user with a continuous wireless connection as the user roams throughout a communications system without requiring any user intervention.
III. Alternate Embodiments
Several aspects of the wireless mobility manager for providing wireless AP handoff and a continuous wireless connection have been described. However, various implementations of the wireless mobility manager provide numerous features including, complementing, supplementing, and/or replacing the features described above. Features can be implemented as part of the wireless station or as part of the AP in different embodiment implementations. In addition, the foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the embodiments of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the embodiments of the invention.
In addition, although an embodiment described herein is directed to a wireless mobility manager, it will be appreciated by those skilled in the art that the embodiments of the present invention can be applied to other systems. In fact, systems for wireless communication fall within the embodiments of the present invention, as defined by the appended claims. The embodiments described above were chosen and described in order to best explain the principles of the embodiments of the invention and its practical applications. These embodiments were chosen to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
Having disclosed exemplary embodiments and the best mode, modifications and variations may be made to the disclosed embodiments while remaining within the scope of the embodiments of the invention as defined by the following claims.
