Method and system for facilitating inter-system handover

Method and system for handover between systems

The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and system that facilitates handover between systems in a wireless communication system.

The prior art cellular wireless communication system, such as the Universal Mobile Telecommunications Service (UMTS) system, contains a plurality of cells with a specific coverage area. When the wireless transmit/receive unit (WTRU) moves across the cell boundary, the wireless transmit/receive unit must be handed over from one cell to another.

Each cell disseminates the information needed to facilitate the handover procedure in the universal mobile telecommunication service system. This information usually includes a list of neighboring cells, which includes a list of neighboring cells near the serving cell. The neighboring cell list allows the wireless transmitting/receiving unit to search only through a finite number of cells instead of all possible codes. As a result, the wireless transmitting/receiving unit can speed up the cell search process and perform handover of new cells more quickly.

At the same time, wireless local area networks (WEANs) based on the IEEE 802.11 standard have been developed and widely used. These systems can expect their high data rate transmission support. An example of the use of wireless local area networks based on the 802.11 standard is the use of so-called "hotspots" access points in public spaces. The wireless transmitting/receiving unit with 802.11 interface can be connected to the hotspot without any physical connection. Once the wireless transmitting/receiving unit is wirelessly associated with the hotspot via a radio frequency interface, the wireless transmitting/receiving unit can transmit and receive data through the hotspot at a data rate that is usually much faster than that provided in the general mobile telecommunication service system.

When hotspots provide high-quality, high-data-rate connectivity, the service range of hotspots The circumference is usually limited to a fairly short distance. Because the transmission power of the wireless transmitting/receiving unit under the 802.11 standard is limited to a relatively low power level, it is difficult to fully cover a large population area. In addition, due to the limited range of 802.11 devices, the wireless transmitting/receiving unit usually performs a fixed search procedure for new hotspots. This is a severe processing load, so the battery of the wireless transmitting/receiving unit is a fixed consumption. Without a mechanism to notify the existence of the hot spot, the wireless transmitting/receiving unit should search for signals transmitted from the hot spot on a regular and continuous basis. This generates unnecessary consumption of processing power and resources.

Because the wireless transmitting/receiving unit can receive relatively high-rate services from hotspots and can maintain connections in a wide range of areas covered by the universal mobile telecommunications service system, it is expected to provide a universal mobile telecommunications service system and wireless that are configured to communicate and handover under the 802.11 standard. Dual-mode wireless transmission/reception unit between local network systems. However, there is currently no convenient method for handing over a cellular communication system such as a general mobile telecommunication service to a wireless local area network communication system such as a hotspot. Therefore, it is expected to provide methods and systems that facilitate the handover between two wireless communication systems such as general mobile telecommunication services and wireless local area networks.

The method that facilitates the handover between systems by the wireless transmitting/receiving unit is disclosed. The wireless transmitting/receiving unit can communicate in multiple wireless communication systems using different wireless communication protocols. The first wireless communication system provides hot spots in at least a part of the area covered by the second wireless communication system. The base station in the cell in the second wireless communication system can generate and transmit a message to notify the wireless transmitting/receiving unit of the existence of a hot spot located near the cell. The wireless transmitting/receiving unit receives the message and is notified There are hot spots near the cell.

The wireless transmitting/receiving unit does not need to search for the signal transmitted from the hot spot and initiates the handover procedure more quickly and effectively.

Here, the term "wireless transmission/receiving unit" includes but is not limited to station, mobile station, user equipment, fixed or mobile subscriber unit, pager or any other type of device that can operate in a wireless environment.

The invention uses different wireless communication protocols to facilitate the handover between two different wireless communication systems. The wireless communication system can be any type of wireless communication system in the future, including but not limited to general mobile telecommunications services, code division multiple access 2000 (CDMA2000), global mobile telecommunications system (GSM), general packet radio service (GPRS) , IEEE802.11 system and Bluetooth.

For the sake of simplicity, the present invention will hereinafter be described with reference to the general mobile telecommunication service system and the IEEE802.11 wireless local area network communication system that provides hotspots in the area covered by the general mobile telecommunication service system. However, as mentioned above, it should be noted that the present invention can also be fairly applied to any wireless access system other than the general mobile telecommunication service system or the IEEE802.11 wireless local area network communication system.

Figure 1 is a block diagram of a wireless communication system 100 according to the present invention. The system 100 includes two or more communication systems operating in different communication protocols and having overlapping coverage areas. Figure 1 depicts a general mobile telecommunication service system 110 and hotspot 120 operating under the 802.11 standard. The universal mobile telecommunication service system 110 has a wider coverage area, and the hot spot 120 has a limited coverage area within the area covered by the universal mobile telecommunication service system 110. The universal mobile telecommunication service system 110 includes service-specific Cover the complex number of cells 112 of the area. Each cell 112 is served by the base station 114, and the hot spot 120 is served by the access point 122.

The wireless transmission/reception unit 130 is configured to communicate in the universal mobile telecommunication service system 110 and the hotspot 120. The wireless transmission/reception unit 130 constantly or regularly monitors the messages from the plurality of base stations 114 and the access points 122. The wireless transmission/reception unit 130 performs the actual measurement of the information received from the cell 112 and the hot spot 120 and can be handed over to another cell 112 or the hot spot 120.

According to the present invention, each base station 114 of the universal mobile telecommunication service system 110 can notify the wireless transmitting/receiving unit 130 of the existence of any hotspot near the cell 112, such as the hotspot 120. The base station 114 of each cell has noticed the existence of the hot spot 120 near each cell 112. The method by which the base station 114 obtains information about the hot spot 120 is not the focus of the present invention. However, for example, the base station 114 can obtain the information by detecting the signal transmitted from the hotspot 120 or by receiving the message from the general mobile telecommunication service system 110 or the wireless local area network system. Alternatively, the base station 114 may be manually configured to include the information when the base station 114 is set up or when a new hot spot is configured.

In the universal mobile telecommunication service system 110, the base station 114 in each cell 112 can generate and disseminate a list of neighboring cells to support effective handover between the cells 112 in the universal mobile telecommunication service system 110. According to the present invention, each cell 112 preferably also includes additional information about the hot spot 120 in the neighboring cell list. Alternatively, the cell 112 can send an independent message for this.

The wireless transmission/reception unit 130 can receive the neighbor cell list or independent information from the base station 114 of the cell 112 serving the wireless transmission/reception unit 130, and be notified that the hot spot 120 near the cell 112 exists. Information package about Hotspot 120 Including but not limited to the location, frequency band, security level of the hot spot 120, or any other information required to establish a connection to the hot spot 120. Because the wireless transmission/reception unit 130 can obtain the connection information to the hotspot 120 in advance, the wireless transmission/reception unit 130 can reduce processing power, place the hotspot, and set any resources normally required for the parameters of the specific hotspot connection.

The connection of the hot spot 120 is preferably propagated from the base station 114 in the cell 112 to all the wireless transmission/reception units 130. Alternatively, the base station 114 of each cell 112 can transmit a list of neighboring cells or independent messages to only a subset of the wireless transmission/reception unit 130 via a dedicated channel or a shared/shared channel.

FIG. 2 is a flowchart of a process 200 that facilitates the handover between systems by notifying the presence of the hotspot 120 to the wireless transmission/receiving unit 130 according to the present invention. The wireless transmission/reception unit 130 is a multi-mode wireless transmission/reception unit, so the wireless transmission/reception unit 130 can receive messages from both the general mobile telecommunication service system 110 and the wireless local area network system (ie, hotspot) 120. The base station 114 in the cell 112 in the universal mobile telecommunication service system 110 can notify the wireless transmission/reception unit 130 in the cell 112 that the hot spot 120 near the cell 112 exists. Information about the hot spot 120 is preferably included in the neighboring cell list. However, this information can be sent via a separate message.

Each base station 114 in the universal mobile telecommunication service system can generate a list of neighboring cells effectively handed over to another cell (step 202). The neighboring cell list contains information required for handover, including but not limited to the coding group of neighboring cells, the main garbled identification or the neighboring cell search window. Each base station 114 transmits the list of neighboring cells to the wireless transmission/reception unit 130 via a transmission channel.

Each base station 114 preferably includes the vicinity of the hot spot 120 in the adjacent cell list Related information, or generate independent information (step 202) and send a list of neighboring cells or information to the wireless transmission/receiving unit 130 located in each cell 112 (step 204). The information related to the hotspot 120 includes, but is not limited to, the location of the hotspot, frequency band, security level, or any other information required to establish a connection to the hotspot.

The information related to the hot spot 120 is preferably disseminated. However, the base station can transmit the information related to the hot spot 120 only to the wireless transmission/reception unit 130 instead of disseminating it. The information can be transmitted via dedicated channels or shared/shared channels.

The wireless transmission/reception unit 130 receives the neighbor cell list or independent message, and is notified of the existence of the hot spot 120 (step 206). The wireless transmission/reception unit 130 does not need to search for signals transmitted from the hotspot 130 and initiates the handover procedure more quickly and effectively.

When the wireless transmitting/receiving unit 130 receives a list of neighboring cells or independent messages, the wireless transmitting/receiving unit 130 may be in an idle mode or an active mode. When the wireless transmission/receiving unit 130 is in idle mode, the wireless transmission/receiving unit 130 can use the hotspot 120 related information to hand over to the hotspot 120, and when the wireless transmission/receiving unit 130 is in the active mode, the wireless transmission/receiving unit 130 can use This information is used via the hotspot 120 to initiate a new call.

Before establishing a connection to the hot spot 120, the wireless transmission/receiving unit 130 performs actual measurement on the information transmitted from the base station 114 and the hot spot 120 in the neighbor cell list (step 208). The actual measurement can be any measurement related to measuring and comparing the signal quality between the cell 112 and the hot spot 120. This may include but is not limited to signal to interference ratio (SIR) or received signal strength index (RSSI).

The wireless transmission/reception unit 130 determines whether the measurement of the message transmitted from the hotspot 120 satisfies a predetermined criterion (step 210). If the measurement meets the criterion, the wireless The transmission/reception unit 130 initiates a handover procedure to the hotspot 120 or initiates a new call via the hotspot 120 (step 212). If the measurement does not satisfy the predetermined criterion, the wireless transmission/reception unit 130 does not attempt to establish a connection to the hot spot 120 (step 214).

Although the features and elements of the present invention are described by the preferred embodiments in a specific combination, each feature or element may be used alone without the other features and elements of the preferred embodiment or with or without other features and elements of the present invention Of various combinations.

<p>100Wireless communication system</p><p>110Universal Mobile Telecommunication Service System</p><p>112complex cell</p><p>114Base station</p><p>120hotspot</p><p>122Access point</p><p>130Wireless transmission/receiving unit</p>

Figure 1 is a block diagram of a wireless communication system according to the present invention.

Figure 2 is a flow chart of processing that facilitates handover between systems according to the present invention.