BACKGROUND

1. Technical Field

The present disclosure relates to cell assignments in cellular networks and more specifically to a system and method of using mobility data about a speed at which a device is moving to make cell handoff assignments.

2. Introduction

Having a mix of large and small cells in Long Term Evolution (LTE) and other networks has the potential for better utilization of scarce wireless spectrum resources. However, when cellular devices connect to cells based on signal strength, the variability in connection quality and increase in rate of handovers can lead to reduced efficiency. The result can make heterogeneous cells into a liability instead of an advantage. As efforts to inter-operate cellular and Wi-Fi networks lead to consolidated networks, Wi-Fi antennas will add to the diversity of wireless access points that can be used.

There is a need and potential advantage of having different types of cells to improve coverage and usage of spectrum, giving rise to heterogeneous networks (“het nets”). There are difficulties in properly executing handovers between different cells in both cases where the cells utilize the same protocol such as LTE or where different cells utilize different protocols such as an LTE cell abutting or overlapping with a Wi-Fi cell.

SUMMARY

The following description relates to a number of different examples of different approaches and systems for handling cell assignments and/or cell handoffs in a cellular environment. The example method relates to making handoff decisions. The method includes receiving mobility data for a device being serviced by a first cell, classifying the device based on a mobility state associated with the mobility data to yield a classification and making a handoff decision when handing off the device from the first cell to a second cell based at least in part on the classification. The mobility state can be computed from the mobility data or estimated from the mobility data. In one example, the classification can be one of slow, medium and fast speed. The classifications or the classes are usually separated by boundaries which can be fixed or variable. For example, a classification can be a speed or a rate of movement of 10-30 MPH. The boundary of 10 MPH at the low end and 30 MPH at the high end can be fixed or variable based on one or more parameters. The boundaries can be re-set.

When the system makes a handoff decision, each classification can include at least one of a preferred cell type and at least one acceptable cell type. The preferred cell type for a slow speed classification can include a micro cell type and a small cell type and an acceptable cell type for the slow speed classification includes a large cell type. The preferred cell type of a medium speed classification can include the small cell type, and the acceptable cell type for the medium speed classification includes the large cell type. The preferred cell type of a fast classification can include the large cell type, and the acceptable cell type for the fast classification includes none.

When making a handoff decision, the device or the system, in one example, can only choose a non-preferred cell type when a received signal is stronger than a higher threshold compared to a threshold required for a preferred cell type. A reselection of a cell can be triggered when the first cell no longer provides a sufficient signal and when the first cell is of a non-preferred type. Handing off can include handing off to the second cell when the second cell is of the preferred type and is suitable.

The classification can include a location in the first cell, potentially of a device, and a path traveled across the first cell. Making the handoff decision can be further based at least in part on a first spectral efficiency of the first cell and a second spectral efficiency of the second cell. Making the handoff decision can further be based at least in part on a bandwidth used by the device and available bandwidth of the second cell.

A system example includes a processor and a computer-readable storage device storing instructions which, when executed by the processor, cause the processor to perform certain operations. The operations include receiving mobility data for a device being serviced by a first cell, classifying the device based on the mobility data to yield a classification and making a handoff decision when handing off the device from the first cell to a second cell based at least in part on the classification.

Another example includes a computer-readable storage device storing instructions which, when executed by a computing device, cause the computing device to perform operations including receiving mobility data for a device being serviced by a first cell, classifying the device based on the mobility data to yield a classification and making a handoff decision when handing off the device from the first cell to a second cell based at least in part on the classification.

A second example relates to making an initial assignment of a device to a service cell. In this example, a method includes receiving mobility data for a device, classifying the device based on a mobility state associated with the mobility data to yield a mobility class and assigning the device to a serving cell based at least in part on the mobility class. The mobility state can be computed from the mobility data or estimated from the mobility data.

When assigning the device to the serving cell, a reselection can be triggered when a first cell no longer provides a sufficient signal and when the first cell is of a non-preferred type. Assigning the device to the serving cell can include assigning the device to a second cell when the second cell is of the preferred type and is suitable.

The mobility class can include one of a location of the device in the serving cell and a path traveled across the serving cell. Assigning the device to the serving cell can further be based at least in part on a spectral efficiency of the serving cell. Assigning the device to the serving cell can further be based at least in part on a bandwidth used by the device and available bandwidth of the serving cell. Assigning the device to the serving cell can further be based at least in part on multiple prioritized lists of cells, each list of the multiple prioritized lists of cells including cells of a same type. In one aspect, cells in a higher priority list are measured more frequently than cells on a lower priority list.

In one possible implementation, the mobile device monitors its serving cell as well as the neighbor cells from the list with the highest priority. If this list (of the highest priority) is of size smaller that a given parameter, the next list is also considered. In another possible implementation, the cells with higher priority are measured more frequently than cells with lower priority. In determining what cell to handover to, cells from a higher priority neighbor list are always considered before those from a lower priority list.

A system aspect of this second example includes a processor and a computer-readable storage device storing instructions which, when executed by the processor, cause the processor to perform operations including receiving mobility data for a device, classifying the device based on a mobility state associated with the mobility data to yield a mobility class and assigning the device to a serving cell based at least in part on the mobility class. A computer-readable storage device aspect of the second example includes a computer-readable storage device storing instructions which, when executed by a computing device, cause the computing device to perform operations including receiving mobility data for a device, classifying the device based on a mobility state associated with the mobility data to yield a mobility class and assigning the device to a serving cell based at least in part on the mobility class.

A third example relates to tracking the distribution of load across cells. Once a system with device classification and assignment to cell types is in place, the system can be monitored to track the distribution of users and load level across cells. If the monitoring detects strong imbalances of cell loads, then, in addition to adjusting the power level of cells, the system disclosed herein makes it possible to dynamically adjust the mobility class boundaries, in order to optimize or improve the spectrum efficiency and capacity of the network.

One example of such a condition is the temporary concentration of slow users in a certain area. Under such circumstances, reducing the value of the class boundaries would allow more users to be classified as more mobile and get preference for being served by larger cells. Another option is to reduce the power of micro cells in the area so that fewer users are assigned to them.

According to this third example, a method is disclosed for balancing cell loads in a network in which a device is classified into a mobility class based on mobility data and the device is assigned to a serving cell based at least in part on the mobility class. The method includes monitoring a distribution of devices and load levels across a plurality of cells to yield an analysis. When the analysis indicates an imbalance of cell loads, the method includes adjusting a boundary of the mobility class. When the analysis indicates an imbalance of cell loads, the method includes adjusting a power level at least one cell of the plurality of cells. When the analysis indicates the imbalance of cell loads, the method further includes performing both of adjusting the power level at least one cell of the plurality of cells and adjusting the boundary of the mobility class. Adjusting the boundary of the mobility class includes one of increasing an upper speed associated with an upper boundary of the mobility class and decreasing a lower speed associated with a lower boundary of the mobility class. Performing one of adjusting a power level at least one cell of the plurality of cells and adjusting a boundary of the mobility class improves a spectrum efficiency of the network relative to a previous spectral efficiency prior to the adjusting of one of the power level and the boundary of the mobility class. It is noted that in radio transmissions, the data (bits) are composed of control bytes as well as content bytes. The closer a device is to an antenna or cell tower, the better the spectral efficiency. When there are handoffs or during a handoff process, there are often more control bytes being transmitted than content bytes.

Performing one of adjusting a power level at least one cell of the plurality of cells and adjusting a boundary of the mobility class improves a capacity of the network relative to a previous capacity prior to the adjusting of one of the power level and the boundary of the mobility class. When assigning the device to serving cell, each mobility class includes at least one of a preferred cell type and at least one acceptable cell type. The preferred cell type for a slow speed classification includes a micro cell type and a small cell type, and an acceptable cell type for the slow speed classification includes a large cell type. The preferred cell type of a medium speed classification includes the small cell type, and the acceptable cell type for the medium speed classification includes the large cell type.

In one example, the device only chooses a non-preferred cell type only when a received signal is stronger than a higher threshold compared to a threshold required for a preferred cell type. When the device is assigned to the serving cell, a reselection is triggered based on one or more parameters or events. For example, the reselection can be triggered when a first cell no longer provides a sufficient signal and/or when the first cell is of a non-preferred type. Assigning the device to the serving cell includes assigning the device to a second cell when the second cell is of the preferred type and is suitable. The mobility class can include one of a location of the device in the serving cell and a path traveled across the serving cell. The device can be assigned to the serving cell based at least in part on multiple prioritized lists of cells, each list of the multiple prioritized lists of cells including cells of a same type.

An example method includes receiving mobility data for a device being serviced by a first cell, wherein the mobility data includes a vector indicating a motion of the device; and classifying the device based on the mobility data to yield a classification. When making a reselection or a handoff decision, a cell type for the classification can include at least one of a preferred cell type and at least one of an acceptable cell type.

An example of a system according to the third example is a system for balancing cell loads in a network in which a device is classified into a mobility class based on mobility data and the device is assigned to a serving cell based at least in part on the mobility class. The system includes a processor and a computer-readable storage device storing instructions which, when executed by the processor, cause the processor to perform operations including monitoring a distribution of devices and load levels across a plurality of cells to yield an analysis and when the analysis indicates an imbalance of cell loads, adjusting a boundary of the mobility class. The system can be a network infrastructure component or a mobile device like a smartphone or cell phone.

A computer-readable storage device example of this third example includes a non-transitory computer-readable storage device or medium that stores instructions which, when executed by a computing device, cause the computing device to balance cell loads in a network in which a device is classified into a mobility class based on mobility data and the device is assigned to a serving cell based at least in part on the mobility class. The instructions causing the computing device to perform operations including monitoring a distribution of devices and load levels across a plurality of cells to yield an analysis and when the analysis indicates an imbalance of cell loads, adjusting a boundary of the mobility class.

