Patent Application
20110130144
The present invention relates generally to the field of wireless communications. More particularly, the present invention relates to facilitating handoff operations in a wireless communication system.
This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
In cellular networks, radio nodes, also sometimes referred to as base stations, access points, cells, Node Bs, eNode Bs, and the like, are normally installed and commissioned after a careful upfront planning and survey process, which is followed by extensive post installation optimization efforts to maximize the network performance. Such optimization efforts usually involve a considerable amount of manual intervention that could include “drive testing” using specialized measurement devices to collect data on network performance at a variety of geographical locations. This data is then post-processed and analyzed to effect optimization steps including power adjustments, antenna tilt adjustments and the like.
Such prior planning, installation and post-installation efforts can become cost prohibitive for networks that cover complicated physical spaces spanning multiple floors of a building, including elevator shafts, stairwells, atria and meeting rooms. In addition, expensive planning, installation and post-installation procedures often do not make business sense for small-cell (e.g., local area) networks that are installed and operated relatively inexpensively. In particular, the cost of installation procedures may be prohibitive in enterprise networks that are described herein, as well as applications that relate to high-density capacity enhancements of a downtown city square and ad-hoc deployment of a cellular network such as in military applications. Nevertheless, proper configuration and optimization of an enterprise network is important for enabling efficient utilization of network resources, as well as conducting operations such as handoffs between and within the networks.
The disclosed embodiments relate to methods, devices, and computer program products that facilitate various handoff operations by providing relevant and up-date-information related to the identity and availability of radio resources within and external to a network. One of the aspects of the disclosed embodiments relates to a method that includes constructing a neighbor list associated with a particular radio node within a network pursuant to an automated network topology discovery. This method further includes receiving information associated with measurements made by user equipment associated with the particular node, and mapping neighboring radio nodes of the particular radio node pursuant to the received information to facilitate a handoff operation.
In one embodiment, the above-noted method further comprises communicating at least a portion of the constructed neighbor list to one or more user equipment. In another embodiment, the automated network topology discovery assesses characteristics of a plurality of radio nodes that are within communication range of the network. In one variation, the plurality of radio nodes comprise radio nodes internal to the network and radio nodes external to the network. According to another embodiment, the constructed neighbor list comprises information indicative as to whether each neighboring radio node is internal to the network or external to the network.
In another embodiment, the constructed neighbor list comprises signaling information associated with each neighboring radio node. In yet another embodiment, the constructed neighbor list comprises information associated with a radio node selected from the group consisting of: a directly scanned radio node, a first-tier radio node, a second- or higher-tier radio node, and a radio node that is suitable for a handoff operation. According to another embodiment, method of claim 1, wherein the communicating of at least a portion of the constructed neighbor list comprises broadcasting or unicasting the portion of the constructed neighbor list.
In one embodiment, the above-mentioned handoff operation is selected from a group of handoff operations consisting of: a soft handoff operation, a softer handoff operation, a hard handoff operation, an inter-radio access technology handoff operation, an inter-frequency handoff operation, and an intra-frequency handoff operation. In another embodiment, where the received information from the user equipment relates to a radio node internal to the network, the radio node internal to the network is selected as a candidate for a soft handoff operation. In still another embodiment, where, the received information relates to a radio node external to the network, the radio node external to the network is selected as a candidate for a hard handoff operation.
According to another embodiment, the above-noted method further comprises receiving information associated with measurements from user equipment associated with other radio nodes internal to the network, and mapping neighboring radio nodes of the other radio nodes.
Another aspect of the disclosed embodiments relates to a method for adding a new radio node to a network. Such a method includes scanning a portion of the network to obtain identities of neighboring radio nodes that are detectable by the new radio node, and constructing a first-tier neighbor list associated with the new radio node. This method further comprises mapping an identifier of the new radio node in accordance with the first-tier neighbor list. In one embodiment, the mapping of the identifier of the new radio node comprises associating a primary scrambling code with an identification information of the new radio node.
According to another embodiment, the above-noted method for adding a new radio node further includes reconstructing a neighbor list associated with at least one radio node other than the new radio node to reflect a presence of the new radio node. In one variation, the scanning of a portion of the network identifies the at least one radio node other than the new radio node. In another variation, the at least one radio node other than the new radio node is a first-tier scanned neighbor of the new radio node, and the reconstructing of the neighbor list comprises updating the neighbor list associated with at least one radio node other than the new radio node to include identification information of the new radio node based on radio frequency reciprocity.
In another embodiment, where the at least one radio node other than the new radio node is a first-tier scanned neighbor of the new radio node, the reconstructing of the neighbor list comprises using the at least one radio node other than the new radio node to conduct a scan of the network. In this embodiment, the reconstructing of the neighbor list also includes updating the neighbor list associated with at least one radio node other than the new radio node to include identification information of the new radio node, if the new radio node is detected as a result of the scan of the network.
According to another embodiment, the identification information of the new radio node comprises at least one of a network controller identity (RNCID), a cell identifier (CID) and a public land mobile network identification (PLMNID). In another embodiment, the above-noted method for adding a new radio node further includes updating the constructed first-tier neighbor list associated with the new radio node to include multiple tiers of neighboring radio nodes. In still another embodiment, such a method additionally includes receiving information associated with measurements made by one or more user equipment.
In one embodiment, at least a portion of the reconstructed neighbor list is communicated to the one or more user equipment. In another embodiment, a mapping of radio nodes is updated pursuant to the received information.
Another aspect of the disclosed embodiments relates to a method for facilitating a hand-in operation from an external entity to a network. Such a method comprises selecting an external radio node associated with the external entity and creating a neighbor list associated with the external radio node, where the neighbor list comprises information associated with one or more candidate radio nodes and such one or more candidate radio nodes are internal radio nodes of the network. This method also includes communicating the neighbor list to the external entity to facilitate the hand-in operation. In one embodiment, the information associated with the one or more candidate radio nodes are obtained pursuant to an automated network topology discovery.
In another embodiment, the neighbor list comprises information associated with first-tier neighbors of the external radio node. In yet another embodiment, the neighbor list comprises information associated with all radio nodes internal to the network. In still another embodiment, the neighbor list is created in accordance with information provided by the internal radio nodes of the network.
According to another embodiment, the above-noted method for facilitating a hand-in operation from an external entity further includes receiving the neighbor list, and creating a constructed neighbor list by the external node. In another embodiment, the communicating of the neighbor list to the external entity comprises broadcasting or unicasting, by an internal network entity, at least a portion of the neighbor list to the external entity.
Another aspect of the disclosed embodiments also relates to a method for facilitating a hand-in operation to a network. Such a method comprises receiving a neighbor list from an entity internal to the network at an external network entity, where the neighbor list comprises one or more candidate internal radio nodes for the hand-in operation. This method also includes receiving a measurement report from a user equipment associated with the external entity, where the measurement report comprising an identifier of an internal radio node. Additionally, the method comprises mapping the identifier to a particular internal radio node on the received neighbor list, producing a hand-in indication and commencing the hand-in operation to the particular internal radio node.
In one embodiment, upon the reception of the neighbor list, a neighbor list associated with an external radio node is updated. In another embodiment, the hand-in indication is received as part of a serving radio network subsystem (SRNS) RELOCATION REQUIRED message. In still another embodiment, the identifier is a primary scrambling code.
Other aspects of the disclosed embodiments relate to devices that are configured to carry out the various operations of the disclosed methods. For example, such devices can include a processor and a memory that includes a processor executable code. The processor executable code, when executed by the processor, configures the device to carry out various operations that facilitate handoff operations.
Additional aspects of the disclosed embodiments relate to computer program products that are embodied on one or more non-transitory computer readable media. Such computer program products comprise computer code for carrying out the operations of the various disclosed embodiments.
These and other advantages and features of various embodiments of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Embodiments of the invention are described by referring to the attached drawings, in which:
In the following description, for purposes of explanation and not limitation, details and descriptions are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these details and descriptions.
Additionally, in the subject description, the word “exemplary” is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. Further, some of the disclosed embodiments are described in the context of an enterprise network. However, it should be understood that the disclosed concepts are equally applicable to other types of networks.
The disclosed embodiments facilitate various types of handoff operations. A handoff, which is sometimes referred to as a handover, refers to the transfer of an ongoing communication session (e.g., a voice or data session) from one radio link to another radio link. The transfer of the on-going session can be to another network (e.g., to a network with a different radio access technology (RAT) or an inter-RAT handoff), to another cell, to another sector of the same cell, to another frequency within the same cell and the like. Additionally, or alternatively, the various handoff scenarios may be described in terms of inter-frequency and intra-frequency handoff operations. Inter-frequency handoff refers to adding a radio link for service to the user equipment on a different logical entity which uses a different channel frequency, such as a neighboring cell operating on a different frequency. Inter-frequency handoff can, but does not necessarily, include terminating the radio link on the source cell (i.e., a hard handoff that is described in sections that follow). Intra-frequency handoff refers to adding a radio link on a different logical entity which uses the same channel frequency. Further, the term “cell” may be construed in different ways. For example, a cell can be considered a logical entity that manages a single radio channel (i.e., the typical definition in the context of Universal Mobile Telecommunications System (UMTS)). In other examples, a cell may be considered a logical entity that manages multiple radio channels, usually on different frequencies. In still other examples, a cell may can be construed as a logical entity that manages multiple radio channels, on the same or different frequencies, that have been sectorized. In other scenarios, a cell can be considered a physical area covered adequately by RF energy from a particular sector of a physical base station installation, which can include just one RF channel or multiple RF channels. In yet other examples, a cell can be construed as a physical area covered adequately by RF energy from all sectors of a physical base station installation, which can also include one or multiple RF channels.
The disclosed embodiments also facilitate different types of handoffs that are known as hard, soft and softer handoffs. In a hard handoff, the connection to the existing radio link is broken before the connection to the new radio link is established. In a soft handoff, the existing radio link is retained and used in parallel with one or more newly acquired radio links of the target cell(s). The simultaneous connections in a soft handoff may be for a brief or substantial period of time. A softer handoff, which is used in Universal Mobile Telecommunications System (UMTS), is a special case of a soft handoff, where the radio links that are used in parallel belong to the same Node B.
A handoff can be initiated for a variety of reasons. For example, a user equipment that moves to another geographical area, which is outside of the coverage area of its existing cell, may initiate a handoff to avoid termination of the on-going session. In another example, a handoff to another cell may be initiated to free up resources at an existing cell. In yet another example, a handoff is used to improve interference from other channels. In order to initiate a handoff, the user equipment must be aware of potential target cells (i.e., neighboring radio nodes) that are likely to accommodate the handoff. The information regarding the neighboring radio nodes are often provided in a listing that is often referred to a neighbor list. In the context of an enterprise network, neighbor radio nodes may include both radio nodes that are internal to the enterprise network and the ones that operate outside of the enterprise network.
The exemplary block diagram that is shown in
It should be noted that while the exemplary radio networks that are depicted in
One of the problems associated with configuration and set up of enterprise networks is that the system is not programmed with the locations of the radio nodes, the desired coverage area of the network, a listing of radio nodes that are considered neighbors of each other for internal handoff purposes, or the relevant external radio nodes (or their signaling parameters) for hand-in/hand-out from/to external networks. Creating the neighbor lists and acquiring information related to network coverage area are not trivial tasks and, as noted earlier, require various measurements, planning and post-installation tuning operations. Traditional macro-cellular approaches require extensive RF mapping and RF planning, drive tests with specialized measurement devices and manual configuration. The manual configuration includes manually configuring the neighbor lists for every radio node in the network.
The disclosed embodiments facilitate different types of handoff operations, including, but not limited to, soft handoffs, intra-frequency hard handoffs and inter-frequency hard handoffs. The disclosed embodiments take advantage of self-configuration techniques that enable an automated discovery of external and internal radio nodes that are connected in a radio frequency (RF) sense. Such self-configuration techniques further allow an intelligent assignment of primary scrambling/spreading codes (PSC) and facilitate the various types of handoffs between and within the networks, all with no, or minimal, manual intervention. The disclosed self-configuration features provide a complete assessment and mapping of the RF environment associated with internal and external radio nodes and accurately identify multiple tiers of neighboring radio nodes, as well as the associated signaling parameters. This discovery of network topology further enables the addition of new cells to the network and allows the propagation of relevant information to an external entity to conduct hand-in operations. It should be noted that in some embodiments a handoff operation may be more specifically described by using the terms “hand-in” and “hand-out.” A hand-in operation is associated with receiving an on-going session that is transferred into the current network from an external network, while a hand-out operation is associated with the transfer of an on-going session out from the current network to an external network.
To enable the various operations that are carried out in some of the disclosed embodiments, the radio nodes within the internal network (e.g., the enterprise network and/or a network that is configured within a larger network) are configured to make measurements of the broadcast transmissions made by other radio nodes within the internal network, as well as in external cells. In particular, broadcast transmissions that are mandated by, for example, UMTS R99, Rels. 5 to 9, as well as future 3GPP standard drafts may be used to acquire the necessary measurement information. The U.S. patent application Ser. No. 12/487,277, titled “METHODS AND APPARATUS FOR COORDINATING NETWORK MONITORING AND/OR AUTOMATING DEVICE CONFIGURATIONS BASED ON MONITORING RESULTS,” which claims the benefit of the filing date of U.S. provisional application No. 61/073,747 filed on Jun. 18, 2008, and is assigned to the present assignee, describes example techniques related to conducting certain measurements through broadcast information transmissions. This application is hereby incorporated by reference in its entirety.
Once the measurements are made, a controller, such as the central controller that is depicted in
It should be also noted that the term internal node or internal radio node are used to refer to radio nodes that are controlled by the internal network. Further, the terms internal cell and internal radio node are sometimes used interchangeably to describe cells with associated radio nodes that are internal to the radio network.
Using the standards-mandated measurement reporting capability of the UEs allows a subset of UEs to be configured to deliver periodic measurement reports to their serving access points. This provides an accurate sampling of the propagation conditions within the deployment region at locations where users are expected to be present. The periodic measurement reporting, unlike events-based reporting, provides an unbiased sampling of the propagation environment, regardless whether the RF conditions are good, bad, changing, or nearly static. Due to the periodic nature of these measurements, however, the data associated with the on-going measurements may become too large for efficient handling and/or storage. The disclosed embodiments address this issue by processing and condensing the information obtained from a number of measurements into a critical set of measurements that is sufficient to assign transmit powers to the access points to satisfy the desired operating conditions. The computational and storage requirements associated with such processing can be kept relatively small by processing the incoming measurement data on-the-fly.
According to another embodiment, the above-noted critical set of UE measurements are processed to produce a set of assigned transmit powers for all access points and to identify possible coverage “holes” in the network. In particular, coverage holes can be identified by noting the locations where a transmit power assignment cannot satisfy the desired operating conditions for a particular critical point. Once the initial power assignment has taken place, the periodic UE measurements may be used to subsequently reassign transmit powers to different access points. Furthermore, subsequent, but infrequent, full scanning may be carried out to refresh the system's knowledge of internal and external cells and neighbors.
Using some or all of the above-noted techniques, together with stored operating and topology information, it is possible to quickly recover from system-wide shutdowns, such as power outages, without repeating the entire topology-discovery and measurement procedures. In addition, since the topology and access point characteristics of the network is known, new access points may be readily added and certain access points may be readily deleted from the network. It should be also noted that the various disclosed embodiments provide a detailed assessment and automated configuration of the access network with no, or little, human involvement. In addition, they provide inter-cell coordination that is necessary to pool and process the collected information to obtain the topology information and optimized parameter settings for the network components.
Referring to back to
The external cell discovery of step 402 can include using a radio node to scan multiple channels (e.g., Universal Terrestrial Radio Access Absolute Radio Frequency Channel Number (UARFCN) downlink channels, hereinafter “UARFCNDL”). Based on the measurements of the multiple channels, a single channel may be designated for use with the radio node. As such, the network may potentially designate a different UARFCNDL for each radio node. For example, multiple UARFCNDL can be assigned to minimize interference between cells on the same UARFCNDL. In one example, the UARFCNDL is assigned to produce maximally spread UARFCNDL values. Such an assignment can be conducted similar to the assignment of PSCs, which will be described in connection with step 406 of
In other embodiments, the same UARFCNDL is assigned to all radio nodes within the network. The assignment of a single UARFCNDL can facilitate soft handoffs in UMTS or CDMA, where only soft handoffs between cells on the same UARFCN are supported. In one example, the particular value of the UARFCNDL is assigned by an operator. In some scenarios, the operator does not have a large number of channels available. For example, only two channel numbers may be available, where one is assigned to the macro network and the other is used for the local or enterprise network. In another example, a single UARFCNDL can be selected pursuant to the scanning and measurement of external signal strengths on each allowable UARFCNDL during the external cell discovery (at step 402 of
Referring back to
As part of the operations in step 404, if a radio node is able to detect the particular PSC, the detecting radio node is considered a first-tier neighbor of the transmitting radio node. In some embodiments, the transmitting radio node is also considered a first-tier neighbor of the detecting radio node due to RF reciprocity. This process may be repeated by placing each radio node, one at-a-time, in operational mode while placing the remaining radio nodes in monitoring mode to identify all the neighbors within the network. It should be noted that an ambiguity may arise if a monitoring access point which had previously detected the PSC during the external discovery process makes the detection during the internal discovery process. In one embodiment, the controller may decide to mark the operational access point as a first-tier neighbor if the newly measured PSC strength exceeds the one found during the external discovery process by a particular threshold.
The neighbors that are produced according to the above operations represent a limited collection of “scanned” neighbors for each radio node that may be placed on a neighbor list associated with that radio node. However, as will be described in the sections that follow, according to the disclosed embodiments, an expanded neighbor list is also constructed (i.e., a “constructed neighbor list”) for each radio node that includes additional neighbors. Such a constructed neighbor list includes the identity and other information associated with multiple tiers of neighbors that can be candidates for a handoff operation. As such, the cells that are listed on a constructed neighbor list are sometimes referred to as a “handoff” neighbor.
In an alternate embodiment, more than one access point may be configured to operate in the operational mode to allow faster internal topology discovery. For example, after a first radio node is placed in the operational mode for a given amount of time, a second radio node is placed in the operational mode. The remaining radio nodes that are still monitoring then determine whether or not they can detect the second radio node that just become operational. If the second radio node is detected, the detecting radio node is considered a first-tier neighbor of the second radio node and, by reciprocity, the second radio node is considered a first-tier neighbor of the detecting radio node. In another variation, a similar detection procedure is carried out while two or more radio nodes with different PSCs are simultaneously placed in the operational mode. The groups of operational access points selected for simultaneous transmission may be chosen, for example, at random or based on the discovered external topology so that they are unlikely to be neighbors.
In describing the various disclosed embodiments, references are made to multi-tier neighbor lists. The following is a simplified example that, with the help of
Returning to the block diagram of
According to an example embodiment, PSC's are assigned to the internal access points according to the following example hierarchy, proceeding serially in arbitrary order through the access points:
(1) A PSC not yet assigned to any access point in the internal network, and one which is not used in the first- or second-tier neighbors.
(2) A PSC assigned to at least one access point in the internal network, but one which is not used in the first- or second-tier neighbors. In case of a tie between two or more PSCs, the PSC that is thus far assigned the fewest number of times to the internal access points is selected.
(3) A PSC used in the second-tier neighbors but not used in the first-tier neighbors. In case of a tie between two or more PSCs that are used in second-tier neighbors, the PSC that was detected by a first-tier neighbor with the smallest common pilot channel (CPICH) RSCP is selected.
(4) A PSC used in the first-tier neighbors. In case of a tie between two or more PSCs, the PSC detected with the smallest CPICH RSCP is selected.
Step 406 in
At the end of steps 406, the topology of the network and the appropriate PSC's associated with each radio node has been determined with zero, or minimal, manual intervention. More specifically, the set of internal radio nodes (i.e., radio nodes within the network), a set of discovered external radio nodes, the first-tier neighbor relationships between the internal and external radio nodes, the PSC's assignments to internal radio nodes, the PSC's associated with external radio nodes, as well as the appropriate signaling parameters for each internal radio node and relevant external radio nodes are discovered. By the way of example, and not by limitation, in a UMTS embodiment, the signaling parameters include a radio network controller identity (RNCID), a cell identifier (CID) that identifies a cell within an RNS, a public land mobile network identification (PLMNID), a channel number (e.g., UARFCNDL) and the like.
Next, in step 408 of
In step 410 of
In step 412 of
Based on the instructions from steps 410 and/or 412 of
In step 416, based on the information received from the user equipment, the internal and external radio nodes are mapped to facilitate handoff operations to/from the appropriate internal or external cells. The following example illustrates some of the operations that may be carried out in step 416. Let's assume that a user equipment has a current Serving Cell X and other cells, Y and Z, in its Active Set. Let's further assume that the user equipment sends a measurement report indicating PSC A is measured with some strength. The controller may then examine the constructed neighbor list associated with cell X, and perhaps with cells Y and Z, to locate a neighbor of cell X (and perhaps Y and Z) with PSC A. If a neighbor cell (e.g. Cell W) with PSC A is listed in one of the constructed neighbor lists, then the controller associates/maps the user equipment's measurement of PSC A with that of cell W. If, on the other hand, a neighbor cell with PSC A is not found within the constructed neighbor list(s), the measurement information associated with the received PSC A can be compared against the information associated with the PSCs on the constructed neighbor list in order to validate the status of existing neighbors and/or to update the neighbor list. For example, a radio node may be added to, or deleted from, a user equipment's Active Set, or a user equipment's Best Cell and/or Serving Cell may be modified. In one scenario in the context of the above noted example, a cell within the system with PSC A may be added to the neighbor list of Cell X. In one embodiment, when the PSCs that are received from the user equipment are mapped to internal radio nodes, the corresponding radio nodes are considered candidates for a soft handoff operations. In another embodiment, when the reported PSCs are mapped to external radio nodes, the corresponding radio nodes are considered for hard handoff operations to an adjacent network.
Steps 408 to 416 facilitate handoff operations of the user equipment for at least the reasons that follow. Cells are internally represented by a unique internal cell handle, or by the unique pair (RNC ID, CID). Communications that are conducted with the core network are carried out using the unique identifier (RNC ID, CID, etc.). However, the user equipment measurements are reported over the air interface with the associated PSCs. These PSCs may be reused throughout the internal network, reused many times throughout the macro network, reused between different enterprise networks, and may be reused between the enterprise network and the macro network. The operations that are conducted in steps 408 through 416 facilitate at least the mapping of the reported PSCs to particular internal or external cell identities (e.g., the PSC is associated with particular RNCID and/or CID of the cells). Further, in embodiments that utilize steps 408 and 412, the user equipment can conduct rapid measurements of the particular PSC's of interest around a serving cell.
The operations of steps 410 through 416 further enhance the utility of the constructed neighbor lists by enabling the inclusion of additional cells (i.e., with particular PSCs that are discovered through the measurement reporting process) on the constructed neighbor lists. In one example, when a new PSC is discovered, the most likely “other” cell in the system with that particular PSC can be selected and added to the constructed neighbor list. In other embodiments, the measurement reports of step 414 can facilitate the removal of cells from the constructed neighbor lists. For example, over time, the system can learn that a particular PSC is not being reported by any user equipment. In such a scenario, the cell associated with that PSC can be removed from the constructed neighbor list. In another example, the system may discover that when a particular cell is added to the Active Set of a user equipment which is in a particular cell, the new radio link is usually or always unreliable or inoperable. In this scenario, that radio node may be removed from the constructed neighbor list.
It should also be noted that the information contained in the measurement reports that are received at step 414 can also facilitate handoff operations in other ways. For example, a user that is in cell A may report the detection of intra-frequency cells C and D in its measurement report, both with similar signal strengths. In a scenario where C is an internal cell and D is an external cell, the system may choose to effect a soft-handover to cell C rather than a hard handover to cell D to minimize the impact on system operations.
As described in connection with step 402 of
In step 604, each access point (that is now in monitoring mode) performs an RF scan that returns detected PSCs and the associated measured signal strengths that are detectable from external networks. This information is received at the controller. In step 606, the controller transmits a command to each access point to successively lock onto each of the detected PSCs and decode the broadcast channel (BCH) of the detected external cell. In an alternate embodiment, the controller does not have to transmit a command to each access point for BCH decoding, but rather each access point autonomously decodes the BCH for any detected PSC. BCH decoding is done in parallel by each of the access points within the internal network. In one example embodiment, instead of allowing all access points to simultaneously perform the decoding, the decoding process may be throttled by allowing only up to N access points to work in parallel.
In an example embodiment, the BCH decode process may be bypassed by having a user/operator provision a set of external cells and their signaling parameters comprising their identities. For example, if each external cell is assumed to have a unique PSC, then this provisioning may be carried out by (a) listing each external cell as a neighbor of every internal cell, or (b) configuring each internal cell to only perform the PSC detection and measurement to discover the neighboring external cells and their (measured) signal strengths.
Referring back to
As noted in connection with step 406 of
In step 808 of
In step 812 of
Utilizing a central controller to conduct the assignments allows coordination and allocation of resources as needed. For example, an area may be covered by possibly selecting a single access point with the smallest pathloss, a single access point that does not have the smallest pathloss (e.g., if that access point needs a high power level to cover a different measurement point), or multiple access points potentially with a lower coverage target (e.g., corresponding to soft handoff gains). Further, the above-noted processes allow automatic identification and designation of coverage “holes” when an inability to cover a measurement point is observed. Moreover, the various embodiments of the present invention may be carried out without the use of central controller, for example, by a peer group of access points.
The disclosed embodiments also facilitate the addition of a cell to an existing network.
In step 906, a first-tier neighbor list for the newly added radio node is constructed. As part of step 906, based on the initially known topology and PSC assignments (which were obtained, for example, through steps 402 to 416 of
In step 908, the neighbor lists for all radio nodes are reconstructed. In one embodiment, the reconstruction of step 608 is carried out by applying RF reciprocity. In this embodiment, it is assumed that if the newly added radio node detects a radio node as a first-tier scanned neighbor with a particular signal strength, then the detected first-tier neighbor would also detect the newly added radio node with the same signal strength. Therefore, the newly added radio node is also a first-tier neighbor of all of its own first-tier scanned neighbors. In another embodiment, upon the addition of a new radio node, the operations described in
In step 910 of
When a radio node is deleted or disabled (rather than added), the inverse operations may be applied. Specifically, the deleted or disabled radio nodes are removed from the detected topology, the neighbor lists are recomputed and updated broadcast and/or unicast messages are sent to the user equipment to reflect the new topology.
The disclosed embodiments can further facilitate hand-in to a network by an external entity by propagating the relevant information to the external entity.
In one embodiment, the neighbor list that is created in step 1004, can comprise one or more “closest” internal radio nodes to the external radio node. The closest internal radio node can be selected based on the internal cell's measured signal strength of the external cell and/or the number of tiers between the internal and the external cell. For example, an internal cell that is a first-tier neighbor of the external cell is considered to be “closer” than an internal cell that is a second-tier neighbor of that external cell. As another example, internal cell A that measures an external cell stronger than internal cell B, is considered to be “closer” to the external cell than internal cell B. In yet another embodiment, the neighbor list that is created in step 1004 can simply include all internal radio nodes known to the network. In still another embodiment, the first-tier neighbor relationships can be populated in a data model and queried via a standard device configuration, such as TR-69 or TR-196.
After the completion of step 1004, the neighbor list can be sent to the external entity (see step 1008). However, in one embodiment, after the completion of step 1004, it is determined, in step 1006, whether more external radio nodes are recognized by the network. If the answer is yes, the process returns to step 1002, where another external radio node is selected and the associated neighbor list is created. Once all external radio nodes have been considered, the process continues to step 1008, where the neighbor lists associated with all recognized external radio nodes are sent to the external entity. The external entity can then use the information provided in the neighbor list(s) to select the proper radio node for conducting a handoff operation.
At step 1106 of
Referring back to
As noted earlier, the mapping of the received PSCs to the internal (or external) cells is done by comparing the newly detected PSCs with the PSCs that are already recognized by the system as corresponding to a particular cell (i.e., a particular RNCID and/or CID). For example, a user equipment's report can indicate the detection of PSC A at signal strength SA, PSC B at strength SB, and so on. In this scenario, the network can check the constructed neighbor list of the user equipment's serving cell in search of an entry with PSC A. If a single match is found, the detected PSC A is mapped to the cell with the associated RNCID and/or CID.
In some embodiments, the above described search operations can produce no matches in the serving cell's constructed neighbor list. In such a scenario, the search can be expanded to include the constructed neighbor lists of the serving cell's neighbors. In other embodiments, the search operation may produce more than one match. That is, multiple radio nodes on the constructed neighbor list may have been assigned to the same PSC. In one embodiment, when multiple matches are found, the detected PSC can be mapped to the cell that is “closest” in RF sense to the serving cell of the user equipment that produced the measurement report. In another embodiment, when multiple matches are detected, all the reported PSC's (e.g., PSC A, PSC B, etc.) and their reported signal strengths (SA, SB, etc.) are used to algorithmically provide a best estimate as to which cell corresponds to the reported PSC.
In another embodiment, the detection of multiple PSC matches are circumvented all together by selectively eliminating multiple listings of the same PSC on a constructed neighbor list. In one example, during the construction of a neighbor list, upon finding multiple listings of the same PSC, only one PSC associated with one radio node is retained. For instance, the radio node that is “closest” to the serving cell is selected. In one example, the lowest tier neighbor cell is selected (e.g., a first-tier neighbor cell is retained over a second-tier neighbor cell). In the event of a tie, the cell that is detected with the highest signal strength is selected.
While some of the exemplary embodiments have been described in the context of a self-configuring and self-optimizing wireless network with multiple radio nodes and one or more central controllers, it is understood that the disclosed embodiments are equally applicable to networks without a central controller (e.g., an autonomous collection of femtocells). In a de-centralized network, direct radio node-to-radio node communications (over the air or through a wired communication link) may be carried out to conduct the various scans, report measurement results and utilize the pooled measurement information to construct the neighbor lists. Similarly, the disclosed embodiments can be applied to hybrid systems that utilize both a central controller and peer-to-peer radio node communications.
These disclosed embodiments can be further extended to a number of different wireless systems with a hierarchical structure that include entities that are functionally equivalent to radio nodes and user equipment. For example, a wireless network where the radio nodes are placed without extensive planning (e.g., mesh networks and/or military field networks) can analogously utilize the disclosed embodiments. In such networks, an installed radio node scans for its neighbors to discover the local topology, differentiates between radio nodes that can coordinate in a cohesive network (i.e., internal radio nodes) against a distinct network (i.e., external radio nodes), sends the discovered topological information to one or more user equipment for conducting measurements, uses the measurement results reported by the user equipment to correlate measurements at the user equipment location with the associated topological neighbors, and informs and enables handoff decisions between a user equipment that is operating with the radio node to a neighboring radio node.
The disclosed embodiments that relate to internal topology discovery and the construction of neighbor lists may further include features that are based on observations of the user equipment behavior in the network. For example, let's assume a user equipment reports a particular PSC in a Measurement Report Message that is not part of the constructed neighbor list of radio node A. Let's further assume that the user equipment's session is subsequently dropped due to bad RF conditions, and that the same user equipment next reappears at radio node B with the reported PSC. In such a scenario, the constructed neighbor list of radio node A can be updated to include radio node B as a neighbor and, similarly, the constructed neighbor list of radio node B can be updated to list radio node A as its neighbor. Furthermore, this modification of neighbor lists may be fed back into the PSC assignment algorithm to account for the “newly discovered” topological change when assigning the appropriate PSCs. As such, the topological map of the network, the neighbor lists and the associated parameters can be modified based on the behavior of the user equipment.
It is understood that the various embodiments of the present invention may be implemented individually, or collectively, in devices comprised of various hardware and/or software modules and components. These devices, for example, may comprise a processor, a memory unit, an interface that are communicatively connected to each other, and may range from desktop and/or laptop computers, to consumer electronic devices such as media players, mobile devices and the like. For example,
The various components or sub-components within each module of the disclosed embodiments may be implemented in software, hardware, firmware. The connectivity between the modules and/or components within the modules may be provided using any one of the connectivity methods and media that is known in the art, including, but not limited to, communications over the Internet, wired, or wireless networks using the appropriate protocols.
Various embodiments described herein are described in the general context of methods or processes, such as the processes described in
The foregoing description of embodiments has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit embodiments of the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. For example, the disclosed embodiments are equally applicable to networks that utilize different communication technologies, including but not limited to UMTS (including R99 and all high-speed packet access (HSPA) variants), as well as LTE, WiMAX, GSM and the like. The embodiments discussed herein were chosen and described in order to explain the principles and the nature of various embodiments and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products.
The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/265,700, titled “METHOD, SYSTEM AND DEVICE FOR CONFIGURING TOPOLOGY OF A WIRELESS NETWORK,” filed on Dec. 1, 2009, the entirety of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61265700 | Dec 2009 | US |
