Traditional cellular wireless networks are deployed as a web of macrocells. The web of macrocells is typically laid out in a uniform grid-like formation, wherein each macrocell has a typical coverage radius of perhaps one to five or more kilometers. The uniform grid-like formation ensures that each macrocell has a common coverage boundary with its neighboring macrocells, with a typical maximum of 6 neighboring macrocells.
Since the macrocells are typically laid out in a uniform grid-like formation, wherein each macrocell typically has a cell radius of one to five or more kilometers in radius, which results in a large coverage area, a network consisting of macrocells has a finite bandwidth of frequency resources, time resources, and code resources (collectively “airlink connection resources”) available to each of an ever increasing number of subscriber devices including, but not limited to cellular telephones, desktop and laptop personal computers, personal digital assistants (PDAs), and other devices that use wireless technology within the macrocells. As the number of subscriber devices increases, there may be extended periods of time where there are insufficient airlink connection resources available to provide the required levels of service to the increased number of subscriber devices. Unavailability of the finite bandwidth of airlink connection resources is experienced, for example, by cellular telephones “dropping” calls and content of web pages on cellular telephones and computers not downloading completely.
Further, in traditional wireless networks, the subscriber devices within each macrocell are provided with a list of neighboring macrocells for handover of services to a suitable neighboring macrocell using a “push” schema. The “push” schema dictates the subscriber devices to continuously scan resources used by the neighboring macrocells for handover purposes. The network uses the scanned measurements to determine when handover incidents should take place. As is known to one skilled in the art, a handover is the changing of a subscriber device's access connection or airlink connection resources from one radio access node (“node”) to another. A handover is typically the result of a mobile subscriber device that leaves the coverage area of one macrocell and enters the coverage area of another. At other times, a handover is done by the network to shift traffic from one macrocell to another if, for instance, one macrocell is more heavily loaded than the other and the subscriber device can receive the required level of service from either. The continuous scanning of neighboring macrocells by subscriber devices for handover purposes also increases the battery drain of the subscriber devices by placing an additional burden on the subscriber devices to process the resources. Furthermore, since macrocells can be added (or deleted) to a coverage area, neighboring macrocells could change. This change results in continually updating the list of macrocells. Continually updating the list and making it available to the subscriber devices is an inefficient schema, especially since the subscriber devices need a complete and correct list in order to “push” services from one macrocell to a suitable other.
Based on the above-described deficiencies associated with traditional wireless networks, there exists a need for a network that addresses the unavailability of the finite bandwidth of airlink connection resources by not only dynamically creating macrocells using an extemporaneous and an “as needed” deployment methodology, but also dynamically creating a plurality of cells smaller in size than macrocells using the same extemporaneous and “as needed” deployment methodology. The plurality of smaller cells are dynamically created within the coverage boundary of each macrocell wherein each smaller cell offers the same bandwidth of airlink connection resources to an ever increasing number of subscriber devices that is available from just the larger macrocells in the traditional wireless networks. There also exists a need for the network to have nodes within the smaller cells to continuously scan resources in use by the other nodes within the same or neighboring cells for handover incidents using a “pull” schema rather than have the subscriber devices continuously scan the resources in use by the neighboring cells for handover incidents using the “push” schema.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
A wireless network for addressing the unavailability of finite bandwidth of airlink connection resources experienced by traditional wireless networks is disclosed. The 3GPP Long Term Evolution (“3GPP LTE”) wireless network is one such network that addresses the deficiencies associated with the traditional wireless networks. According to one embodiment, the macrocells are not deployed in a uniform grid-like formation, but rather using a dynamic extemporaneous and an “as needed” deployment methodology. According to another embodiment, a plurality of smaller cells is created within the coverage boundary of a macrocell. Each smaller cell within a macrocell is capable of providing to the subscriber devices the same bandwidth of airlink connection resources available from the macrocell. According to another embodiment, each smaller cell is dynamically created to load balance the bandwidth of airlink connection resources due to an increase in the number of subscriber devices or an increase in the resources usage by the subscriber devices.
The wireless network further addresses the prior art inefficient “push” schema for handover of network services of a subscriber device from one node to another. According to one embodiment, nodes within each of the plurality of smaller cells continuously scan subscriber devices actively connected to other nodes for handover of services of a subscriber device using a “pull” schema. According to another embodiment, the nodes are capable of continuously scanning other nodes to measure resources used by the other nodes. The measurement tells the nodes if they are capable of providing to a subscriber device within the same or neighboring cell at least a minimum grade of service required by the wireless network. If a node is capable of providing the at least minimum grade of service, the node informs the node currently serving the subscriber device. According to one embodiment, the node currently providing the airlink connection resources to the subscriber device can request the subscriber device to check if the measurement made by the node requesting the handover is mutually valid. If the measurement is mutually valid, the node currently providing the services to the subscriber device initiates the handover to the requesting node.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
In the following description, numerous specific details are set forth to provide a more thorough description of the illustrative embodiments of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without these specific details. In other instances, well known features have not been described in detail so as not to obscure the invention.
Returning to
Network layer 220 houses one or more servers, for example the P-GW and MME/S-GW class servers for delivering the content from network layer 210. Servers within the core network layer communicate with one or more nodes within the access network layer 240 via known interfaces, for example the S1 interface and between each other via other known interfaces, for example the S5 interface. Access network 240 illustrates two nodes, namely, node 240A that is an eNodeB and node 240B that is another eNodeB. Nodes 240A and 240B are interconnected with each other via known interfaces, for example the X2 interface. Access network 240 comprises a plurality of access nodes (“smaller cells”) within its coverage boundary. These smaller cells range in a coverage area spanning from 600 meters for microcells to about 200 meters for picocells to about 60 meters for femtocells. As noted, each of these smaller cells offers the same bandwidth of wireless airlink connection to the subscriber devices available from just the macrocells in the traditional wireless networks.
Finally, network layer 250 houses the plurality of subscriber devices 250A, 250B . . . 250N. As noted, subscriber devices include, but are not limited to cellular telephones, desktop and laptop personal computers, PDAs, and other devices that use wireless technology. Subscriber devices 250A, 250B . . . 250N can request content information from the network layer 210 or from the network layers of the traditional networks (not shown) that house services specific to that network. When subscriber devices 250A, 250B . . . 250N request content from network layer 210, nodes 240A or 240B are the nodes that would service that request. Similarly, when the subscriber devices 250A, 250B . . . 250N request content from the network layer of traditional wireless networks that house services specific to that network, nodes 240A or 240B are the nodes that would service that request using known interfaces (not shown).
As noted, there is a plurality of smaller cells within the coverage boundary of a macrocell. According to one embodiment, these smaller cells are dynamically created to load balance the bandwidth of airlink connection resources available using an extemporaneous and an “as needed” deployment methodology. Each of these smaller cells offers the same bandwidth of airlink connection to subscriber devices available from just the macrocells in the traditional wireless networks.
As noted, nodes, i.e., candidate nodes may continuously scan for signals transmitted by subscriber devices actively connected to other nodes for handover of services of a subscriber device. Accordingly, in operation, candidate node N2 continuously scans or “pulls” information of services from subscriber devices including SD for handover of services from serving node N1. Uplink signals sent from SD to N1 are received at N2 via uplink communications path, UL1. N2 processes, or measures, these signals to determine current resource needs of SD.
Candidate nodes may also continuously scan for signals transmitted by serving nodes actively connected to subscriber devices for handover of services of a subscriber device. Accordingly, in operation, candidate node N2 continuously scans or “pulls” information of services from serving nodes including N1 for handover of services from the serving nodes. Downlink signals sent from N1 to SD are also received at N2 via downlink communications path, DLL In this case, N2 is equipped with a receiver that allows it to receive and process, or measure, these signals to determine current resource needs of SD.
If a measurement taken from either the uplink signals or downlink signals leads to the conclusion that N2 is able to provide the at least minimum grade of service to SD, N2 sends message M1 to serving node N1 informing N1 of the conclusion. If N1 asserts that the conclusion is in fact true, N1 hands over services of SD to N2. N2 then continues as the new serving node by providing uninterrupted services to SD without SD's involvement in the handover of services from N1 to N2.
For example, at
As noted, nodes in a 3GPP LTE wireless network are interconnected via the X2 interface. The nodes use the X2 interface to share information regarding their resource usage within a spectrum of airlink connection resources. Each node receives and is capable of processing more resources than used by the cell within which it lays. For example, node 240A within larger cell 240. The unused resources maybe in use by other nodes. Since a node has knowledge of the resources being used by the other nodes, it is capable of making a measurement of the other node's resources for a potential handover.
Resources exist in both the time domain and the frequency domain.
The unused resource blocks may not be idle, but could be used by the other nodes within a cell, as the same spectrum is shared amongst the plurality of nodes of the given cell. So, even though the node receives all available resource blocks, the node only uses the ones marked R1, R2 . . . RX. There may be several reasons for a node to not use all available resource blocks including, but not limited to too much interference or lack of need to serve the required load. Since the node has knowledge of which resources are being used by the other nodes. i.e., resource blocks marked RA, RB . . . RN, it is capable of making a measurement of the other node's resources and using this measurement to assert handover.
As noted, a handover is the changing of a subscriber device's access connection or airlink connection resources from one node to another. A handover is typically the result of a moving subscriber device that leaves the coverage area of one cell and enters the coverage area of another. At other times, a handover is done by the network to shift traffic from one cell to another if, for instance, one cell is more heavily loaded than another and the subscriber device can receive the required level of service from either. According to aspects of the disclosed subject matter, there exists yet another handover deployment situation. This situation arises when a smaller cell, for example a femtocell, is overlaid by a larger macrocell that uses an air interface access technology different than 3GPP LTE. The different air interface access technology could be, for example, the Global System for Mobile Communications (“GSM”) interface or the Universal Mobile Telecommunications System (“UMTS”) interface. In any case, the smaller cell must have the capabilities for receiving resources from these other interfaces in addition to receiving resources from the 3GPP LTE air interface. There is an inter-radio access technology (“inter-RAT”) function within the core networking layer, for example Network layer 220 at
Once a node, i.e., candidate node, has taken a measurement of the other node's resources and asserts that it can provide at least a minimum grade of service as required by the wireless network to a subscriber device than a node currently serving the subscriber device, i.e., serving node, the candidate node informs the serving node that it is capable of providing the at least minimum grade of service as required by the wireless network, i.e., it requests a handover of the subscriber device's services. According to one embodiment, the serving node can request the subscriber device to check if the assertion made by the candidate node is mutually valid. If the measurement is mutually valid, the node currently providing the services to the subscriber device initiates the handover to the candidate node. If the measurement is not mutually valid or if the node requesting the handover is found to be unsuitable, maybe because the subscriber device has moved in the interim to a different location or its needs have changed, the subscriber device continues to receive its resources from the serving node.
At this juncture, the serving node can request the subscriber device to check the measurement taken by the candidate node requesting the handover. This request is made at block 740. Next, at block 745, the subscriber device checks to see if the assertion by the candidate node is mutually valid. If the assertion is not mutually valid (arrow from block 745 marked “NO”), at block 750 the subscriber device continues to receive its resources from the serving node and the flow stops at block 770. If, on the other hand, the measurement is mutually valid (arrow from block 745 marked “YES”), at block 755 another check is made to see if the candidate node is a suitable node. If the candidate node is not a suitable node (arrow from block 755 marked “NO”), for example if the subscriber device has moved to a new location or if the subscriber device's needs have changed in the interim, the flow continues to block 750 after which the flow stops at block 770. If, on the other hand, the candidate node is a suitable node, at block 760 the serving node initiates the handover to the candidate node. At block 765, the subscriber device gets its resources from the candidate node, which is now the serving node and the flow stops at block 770. Since a node requests handover rather than the subscriber device, which it does by continuously scanning resources in use other nodes, or a “pull” schema, the network successfully addresses the prior art inefficient “push” schema for handover of services of a subscriber device from one node to another.
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosed subject matter. Thus, while preferred embodiments of a network that addresses the unavailability of the finite bandwidth of airlink connection resources and for the network to have nodes that continuously scan resources in use by other nodes for handover incidents using a “pull” schema are described herein, it is to be understood that the embodiments of the disclosed subject matter are not limited to the described network and methods but rather by the following claims and their full scope of equivalents.
This application claims the benefit of U.S. Provisional Patent Application No. 61/155,107, titled “Neighboring Cell Directed Handover In A Wireless Network” filed Feb. 24, 2009, the disclosure of which is hereby expressly incorporated by reference, and the filing date of which is hereby claimed under 35 U.S.C. §119(e).
Number | Name | Date | Kind |
---|---|---|---|
20050221827 | Natsume | Oct 2005 | A1 |
20070213067 | Li et al. | Sep 2007 | A1 |
20080064401 | Forssell et al. | Mar 2008 | A1 |
20080318576 | So et al. | Dec 2008 | A1 |
Number | Date | Country | |
---|---|---|---|
61155107 | Feb 2009 | US |