Wireless station and method for implementing a media independent handover

The present invention generally relates to wireless communication systems. More specifically, the present invention relates to methods and systems for implementing media independent handovers between different wireless network types.

A typical mobility system has two main modes of operation: idle mode and connection mode. In idle mode, the STA (station) feature does not include user services (ie, ongoing calls or transactions), but includes paging channel monitoring, available service request channels, and receivers. 100% is available for downlink measurements in wireless environments, background adjustments, unscheduled APs (access points), and / or technology reselections. In connected mode, STA features include active user services (eg, in-progress calls), allow handovers, and use of restricted receivers for measurements (because user services prioritize). , And fully coordinated scheduled APs and / or technical handovers.

Before entering idle mode (eg at boot time), the STA must make a selection to determine the best AP and technology available for the requested user service. During idle mode, the STA continuously examines adjacent APs and APs with different technologies. When deciding on a "better" AP, the STA moves to the new AP (ie, "reselects").

During the connection mode, the handover moves from one AP to another that provides "better" service. This includes switching to APs using different techniques. In the idle case, the handover occurs without significant interference with the active user service.

One purpose is to achieve seamless handover between different wireless network types, such as between different WLAN (Wireless Local Area Network) types, or between WLANs and cellular systems (ie, allowing STA movement). Is.

Figure 1 shows the existing cellular mobility model 100, a centralized RRM (radio resource management) approach to mobility issues. The cellular STA102 (eg, a second generation mobile device or a third generation user device) is a mobile device that can move freely among a plurality of AP104s. AP104 may include, but is not limited to, a GSM base station and FDD / CDMA node B. AP104 is connected together via wireless network 106. When the STA102 is moving around, the HPF (handover policy function) 108 is used to guide the STA102's handover in the AP104. The HPF108 is centrally located (eg, in a 2nd generation BSC (base station controller) or 3rd generation RNC (radio network controller)) and network 110 (eg in a 3rd generation radio network controller). , Switching device or server).

The HPF108 provides adjustments when the STA102 moves to a different AP104. The STA102 sends the measurements to the HPF108, which makes the handover and the final decision as to which AP104 the STA102 should turn on.

Semi-static frequency allocation is made for each AP104 in model 100, requiring some radio schemes. In idle mode, AP selection / reselection decisions for both intra-technology (eg, GSM to GSM) and inter-technology (eg, GSM to FDD / WCDMA) are made by STA102 and by HPF108 (from network 110). ) Supported by system information. In connection mode, the AP handover decision is made at HPF108 and is supported by measurements made by STA102 and transmitted to HPF108 via L3 signaling.

Figure 2 is a diagram of the existing WLAN Mobility Model 200 showing a distributed RRM approach to mobility problems. The 802.xSTA202 is free to move within multiple AP204s and includes, but is not limited to, 802.11a and 802.16 APs. AP204 communicates with network 208 (eg, a gateway or router) via wireless network 206.

In model 200, dynamic frequency assignment is made for each AP204 and no radio design is required. The only type of handover supported in the mobility model 200 is intra-technology (eg 802.11a to 802.11a) idle mode handover, where AP selection / reselection decisions are automatically determined by the STA202. To. Other types of handovers (idle mode with intertechnology and connection mode) are not supported in the mobility model 200.

In this distributed RRM approach, APs can be placed anywhere and APs can manage themselves dynamically. There is no centralized point where RRM works, so none of the elements in the architecture perform a handover.

Figure 3 is a diagram of existing mobility system architectures for cellular and WLAN network types. GPRS (2nd Generation) STA300 includes Physical Layer 302, Data Link Layer 304, and Network Layer 306. The data link layer 304 includes a MAC (media access control) sublayer 310 and an RLC (radio link control) sublayer 312. Network layer 306 includes GSM RR (radio resource) manager 314, MM (mobility management) protocol manager 316 and IP (Internet Protocol) / convergence manager 318.

The 3GPP (3rd Generation) STA320 includes a physical layer 322, a data link layer 324, and a network layer 326. The data link layer 324 includes a MAC sublayer 330 and an RLC sublayer 332. Network layer 326 includes 3G RR controller 334, MM protocol manager 336 and IP / convergence manager 338.

802.xxSTA340 includes physical layer 342, data link layer 344 and network layer 346. The data link layer 344 includes a MAC sublayer 350 and an LLC (logical link) sublayer 352. Network layer 346 includes mobility IP manager 354 and IP / convergence manager 356.

The RR manager / controller (314, 334) manages the immediate wireless link, the handling of all information about the wireless link. The MM protocol (316, 336, 354) deals with network-level issues (ie, issues other than the call itself), such as registration and location updates as the STA moves through the system.

<p num="0016"> Current WLAN systems offer only limited mobility capabilities. User transitions for intra-technology (eg, 802.11 to 802.11) and inter-technology (802.11 to 802.11) can be characterized as reselective behavior as opposed to handover behavior in common full mobility systems (eg, GSM). It is supported using a "break before make" strategy. This issue is limited to the growth of WLAN technology, as this approach is not sufficient to support real-time services such as audio and video streaming.</p>

<p num="0017"> The present invention is a solution for implementing a complete mobility solution for both intra-technology and inter-technology transition scenarios, satisfying the requirements of both real-time and non-real-time services. The present invention is a device-agnostic handover policy function that places few restrictions on the physical implementation. The present invention supports the transition from WLAN to WLAN as well as the transition from WLAN to wired LAN, and integrates with a general mobile cellular system (eg GSM) to realize a fully mobile WLAN / cellular solution. to enable.</p><p num="0018"> Systems that implement media-independent handovers in stations of wireless communication systems include physical sublayer management entities, media access control sublayer management entities, management information bases, and handover policy functions. The handover policy function can receive measurements and system information from physical sublayer management entities, media access control sublayer management entities, and management information bases . Then, the handover policy function automatically determines whether or not the handover should be executed.</p><p num="0019"> The system implements media-independent handover in a wireless communication system with stations and access points. The station includes a physical sublayer management entity, a media access control sublayer management entity, and a MIH (media independent handover) layer. The MIH layer communicates with physical sublayer management entities and media access control sublayer management entities. The access point includes a handover policy function that communicates with the MIH layer and determines whether the station should perform a handover.</p><p num="0020"> A method for implementing media-independent handover in a station in a wireless communication system is initiated by providing a handover policy function. System measurements and information are provided by the station to the handover policy function. The determination of whether or not to execute the handover is based on system measurement and information.</p><p num="0021"> Methods for implementing media-independent handovers in wireless communication systems begin by providing a MIH (media independent handover) layer at the station and by providing a handover policy function at the access point. Station measurements are transmitted from the station to the access point via the MIH layer. The handover policy function determines whether or not the station should perform a handover. Handover is controlled via information transmitted via the MIH layer.</p><p num="0022"> Stations that implement media-independent handovers in wireless communication systems include physical sublayer management entities, media access control sublayer management entities, management information bases, and handover policy functions. The handover policy function can receive measurements and system information from physical sublayer management entities, media access control sublayer management entities, and management information bases. Then, the handover policy function can automatically determine whether or not to execute the handover.</p><p num="0023"> Integrated circuits for implementing media-independent handovers in stations in wireless communication systems include physical sublayer management entities, media access control sublayer management entities, management information bases and handover policy functions. The handover policy function can receive measured values and system information from physical sublayer management entities, media access control sublayer management entities, and management information bases. Then, the handover policy function automatically determines whether or not the handover should be executed.</p><p num="0024"> A more detailed understanding of the present invention will be obtained from the following description of the preferred embodiments given by way of example and will be understood with the accompanying figures.</p>

<figref num="1">It is a figure of the conventional cellular mobility model.</figref><figref num="2">It is a figure of the conventional WLAN mobility model.</figref><figref num="3">Mobility system architecture for traditional cellular and WLAN network types.</figref><figref num="4">It is a figure which shows the mobility architecture in WLAN by this invention, and how it compares the kind of a cellular network.</figref><figref num="5">It is a figure of the WLAN mobility model by this invention.</figref><figref num="6">It is a figure which shows the structure of the STA architecture which implemented the distributed handover policy function of this invention.</figref><figref num="7">It is a figure which shows the structure of the STA architecture which implemented the centralized handover policy function of this invention.</figref>

In the following, the term "station" (STA) includes, but is not limited to, wireless transceivers, user devices, fixed or mobile subscriber devices, pagers or any other type of device that can operate in a wireless environment. .. In the following, the term "AP (access point)" includes, but is not limited to, a base station, node B, site controller, or other type of interface device in a wireless environment.

FIG. 4 is a diagram showing the mobility architecture in WLAN and how it compares cellular network types. GPRS STA300 and 3GPP STA320 are identical to the STAs described in connection with FIG. 802.xxSTA400 includes physical layer 402, data link layer 404 and network layer 406. The data link layer 404 includes a media access control sublayer 410 and a link layer control sublayer 412. Network layer 406 includes media independent handover layer 414, mobile IP manager 416 and IP / convergence manager 418. The rest of the discussion will focus on MIH (media independent handover) layer 414 and how it works in the mobility model. MIH layer 414 performs similar functions as GSM RR314 and 3G RRC334.

Figure 5 shows the WLAN mobility model 500 according to the invention, showing two basic HPF options: distributed and centralized. These options relate to situations that were not previously addressed by the mobility model, namely idle mode handovers and connection mode handovers in intertechnology.

The 802.xSTA502 is a free mobile among multiple AP504s and can include, but is not limited to, 802.11a and 802.16AP. AP504 communicates with network 508 (eg, gateway or router) via wireless network 506.

Model 500 can implement distributed HPF510 in STA502 and / or centralized HPF520 in network 508.

In setting the distributed HPF, the STA automatically makes selection, reselection, and handover decisions. This includes idle mode, inter-technology selection / reselection and both connection mode handover types.

In setting the centralized HPF, the HPF located on the system side assists the selection and reselection process and makes a handover decision supported by the information gathered by the STA. Information is communicated from the STA to the HPF via the signaling mechanism of the present invention (ie MIH layer). This includes idle mode, inter-technology selection / reselection and both connection mode handover types.

FIG. 6 is a block diagram of a functional architecture for the STA600 using the distributed HPF of the present invention. The STA600 includes a physical sublayer ME (management entity) 602 and a MAC sublayer ME604. The HPF606 communicates with both the physical sublayer ME602 and the MAC sublayer ME604. When making a handover decision, the Local Management Information Base (MIB) 608 stores the information accessed by the HPF606. The physical sublayer ME602 includes a PLCP (physical layer convergence procedure) sublayer 610 and a PMD (physical medium dependant) sublayer 612. MAC sublayer ME604 includes MAC sublayer 614.

The reselection and handover decisions are automatically determined by the STA600. The HPF606 receives measurements and other events (commonly used information in making handover decisions) from the MAC sublayer ME604 and the physical sublayer ME602. The HPF606 processes this information and makes a voluntary decision as to whether or not to perform a handover.

This is a limited handover solution, which is really just an extension of the reselection procedure and is so characterized in a typical mobility system. This is appropriate, but it is a secondary solution, mainly because it uses the "break then make" strategy. With this strategy, when the STA recognizes that this radio link is down, the STA either disconnects the current link or loses the link independently before a new link is established. The availability of resources to complete the handover is not guaranteed and will result in dropped calls by the new AP, which lacks the resources to allow the handover. Possibility of call loss is a sufficient solution for non-real-time services, but an unacceptable solution for real-time services such as voice communication. Moreover, in the same sense, that is, in the sense that performance will suffer as more STAs are added to the system, this is a poorly scalable solution.

Figure 7 is a block diagram of the functional architecture for the STA700 using a centralized HPF. The STA700 includes a physical sublayer ME702 and a MAC sublayer ME704. The MIH (media independent handover) layer 706 communicates with both the physical sublayer ME702 and the MAC sublayer ME704. The MIH layer 706 communicates with the MIH layer 708 on the system side. MIH layer 708 communicates with system HPF710. The physical sublayer ME702 includes a PLCP sublayer 712 and a PMD sublayer 714. MAC sublayer ME704 includes MAC sublayer 716.

The MIH layer 706 and the system HPF710 communicate via the MIH layer 708. The MIH layer 706 sends the measurements to the HPF710, which sends the system information to the MIH layer 706. Reselection and handover decisions are coordinated between MIH Layer 706 and HPF710 based on this information exchange. The use of both MIH Layer 706, MIH Layer 708 and HPF710 is similar to cellular system type handovers.

Reselection and handover decisions are coordinated by the HPF710 and supported by measurement reporting and system signaling received via MIH layers 706, 708. This is a fast and appropriate handover solution that is driven by making centralized decisions, guarantees resource availability to create and then disconnect, and complete handovers. This is a sufficient solution for non-real-time services, an acceptable solution for real-time services, and easily extensible to provide a complete mobility solution.

Both mobility protocols (eg, MM, Mobile IP, SIP) and resource control protocols (eg, RRC or MIH layers) are required to support a complete mobility solution. Mobility protocols support discovery, registration, tunneling, termination (or paging), and network-level handover and security (between two switches). Resource control protocols provide functions such as system information, termination (or paging), cell selection / reselection, establishment, opening, measurement reporting, power control and radio-level handover (between two radios). to support. Handover support provided at both levels is required to support a complete mobility solution.

On the network side, both MIH Layer 708 and HPF710 can be located in any centralized entity such as an AP, server, database or router. In a preferred embodiment, the MIH layer 708 and HPF710 are placed on the AP or AP controller. MIH Layer 708 and HPF710 are separate logical entities. MIH Layer 708 acts as a state machine, collects the necessary information and passes it to the HPF710. The HPF710 makes a handover decision based on the received information.

Although the present embodiment has been described from the viewpoint of WLAN, the principle of the present embodiment can be similarly applied to any kind of wireless communication system. The centralized HPF architecture can be extended to support wireless-to-wire interworking scenarios such as handover policies when connecting wireless devices to wired systems. In this example, when using an 802.11 capable laptop, the laptop is coupled to the docking station and handed over to take advantage of the Ethernet® connection coupled to that laptop's docking station. To use.

The elements shown in Figures 6 and 7 are depicted as separate elements, but these elements are single ICs (integrated circuits) such as ASICs (application specific integrated circuits). It can be implemented in multiple ICs, individual components, or a combination of individual components and one or more ICs. In certain implementations, the functionality of embodiments and features of the invention can be placed in individual components / ICs and can be partially / totally disabled or stopped.

Although the features and elements of the invention have been described in preferred embodiments in a particular combination, each feature and element may be described alone (without other features and elements of the preferred embodiment) or other of the present invention. It can be used in various combinations with or without features and elements.