Capacity Optimisation in a Cellular Wireless Network

• US 20090046665A1
• Filed: 12/28/2007
• Published: 02/19/2009
• Est. Priority Date: 08/16/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Jeffries, Andrew, Harl, Steven, Steven, Donald, Axis, Simon, Robson, Julius, Boue-Lahorgue, Mathieu
• Granted Patent: US 8,537,774 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

Embodiments of the invention relate to cellular wireless networks and are particularly suited to networks including different types of base stations. So-called femtocell base stations are typically deployed within a subscriber'"'"'s premises and operate at low transmit power, providing a very limited area of wireless coverage. A femtocell is typically deployed within the area of wireless coverage of a conventional macrocell type of base station, and if handover from a macrocell is performed on the basis of the best signal to noise plus interference ratio, a connection is likely to be transferred to another macrocell rather than to a femtocell. However, in view of the low density of user equipments capable of transceiving with a femtocell, the femtocell could potentially provide a greater data rate to the user equipment terminal than is possible with a macrocell. A cellular wireless network according to an embodiment of the invention employs a method of handover algorithm that has dependence on both a measure of signal quality such as signal to noise plus interference ratio and on a measure of loading of the base station. The handover algorithm is thereby able to weight selection of a base station on the basis of data rate, and intelligently engineer handover to a femtocell.

Claims

1. In a radio communications network comprising a first base station, a second base station and a first user equipment terminal, a method of optimising downlink data rate available at the first user equipment terminal, the method comprising the steps of:

receiving first and second measures of signal quality of radio communications received at the first user equipment terminal from the first and second base stations respectively;

receiving first and second measures of loading of the first and said second base stations respectively, wherein the first and second measures of loading relate to radio resource or to backhaul resource;

selecting the first or second base station for transmission of a data packet to the first user equipment terminal in dependence on the first or second measures of signal quality and the first or second measures of loading.

2. A method according to claim 1, wherein the first base station is of a first type and the second base station is of a second type, different from the first type.

3. A method according to claim 2, wherein the first type of base station is a macrocell type and the second type of base station is a femtocell type.

4. A method according to claim 1, wherein the second base station has an area of cellular wireless coverage within an area of cellular wireless coverage of the first base station.

5. A method according to claim 1, including transmitting a message comprising a plurality of said data packets, wherein said selecting of a base station is performed for individual ones of said data packets.

6. A method according to claim 1, in which said selecting is performed in dependence on a service being provided or requested to be provided to the first user equipment terminal.

7. A method according to claim 1, wherein the first and second measures of the signal quality comprise or are derived from a measure of strength of signals received from the first and second base stations respectively at the first user equipment terminal.

8. A method according to claim 1, wherein the first and second measures of the signal quality comprise or are derived from a measure of signal to noise ratio or from a measure of signal to noise plus interference ratio of signals received from the first and second base stations respectively at the first user equipment terminal.

9. A method according to claim 1, wherein the first and second measures of loading comprise or are derived from measures of radio resource loading of the first and second base stations respectively.

10. A method according to claim 1, wherein the second measure of loading comprises or is derived from a measure of backhaul loading of the second base station.

11. A method according to claim 1, wherein the first and second measures of loading comprise measures of loading current when performing said selecting of a base station.

12. A method according to claim 1, wherein the first and second measures of loading comprise predicted measures of loading.

13. A method according to claim 1, wherein the first and second measures of loading comprise a number of circuits allocated to user equipment terminals on a downlink from each respective base station to the user equipment terminals.

14. A method according to claim 1, wherein the first and second measures of loading comprise a number of streams carried by the respective base station multiplied by the mean data rate of a respective stream.

15. A method according to claim 1, wherein the first and second measures of loading comprise the number of user equipment terminals maintaining a respective base station as part of an active set of servers.

16. A method according to claim 1, wherein the first and second measures of loading comprise the number of active user equipment terminals being served by a respective base station.

17. A method according to claim 1, wherein the first and second measures of loading comprise a size of a queue of data packets at a respective base station.

18. A method according to claim 1, wherein the first and second measures of loading comprise a measure of latency of packets at a respective base station.

19. A method according to claim 1, wherein the first and second measures of loading comprise a measure of an average data rate being provided to active user equipment terminals communicating with a respective base station.

20. A method according to claim 1, wherein the first and second measures of loading comprise a measure of a proportion of radio resource that could be offered to a user equipment terminal newly attaching to a respective base station.

21. A method according to claim 1, wherein said selecting is based on a measure of the user equipment terminal velocity or direction.

22. A method according to claim 1, wherein a base station is selected which would be expected to offer the first user equipment terminal a higher effective data rate if the first user equipment terminal were to be re-pointed to it.

23. A method according to claim 1, wherein a base station is selected on the basis of overall data rates provided by a respective base station to both the first user equipment terminal and at least one other user equipment terminal if said other user equipment terminal were to be handed over to it.

24. A node of a radio communications network arranged to perform the method of claim 1.

25. A radio communications network arranged to perform the method of claim 1.