# Patent

## Title
Method and system architecture for a self organizing network

## Abstract

A method and system architecture for a self-organizing network (SON) includes a first cell having a first user equipment classifier for determining one of cell edge and cell central. The SON also includes a second cell having a second user equipment classifier for determining one of cell edge and cell central. The system architecture and method provide a first transmit time interval (TTI) schema for user equipment within the area of coverage associated with the first cell and a TTI schema for user equipment within the area of coverage associated with the second cell, the second TTI schema differing from the first TTI schema. The user equipment is classified as cell center or cell edge in dependence upon at least one of QoS requirement, geometry, periodic PSMM and CQI reports. The TTI schemas are used for “cell edge” user equipment by the respective cells.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. application Ser. No. 14/853,550, filed Sep. 14, 2015, which in turn is a continuation of U.S. application Ser. No. 13/092,140, filed Apr. 21, 2011, now U.S. Pat. No. 9,137,684, issued Sep. 15, 2015, which application in turn claims benefit of priority from U.S. Provisional Application No. 61/326,411, filed Apr. 21, 2010, which are hereby incorporated by reference in their entirety as if fully set forth.


FIELD OF INVENTION
The present invention relates to methods and system architectures for Self Organizing Network (SON) and is particularly concerned with wireless network performance that is subject to intercell interference.
BACKGROUND OF THE INVENTION
This section is not to be construed as reflecting an admission that any content herein is relevant prior art. Moreover, this section is not an indication of a search for relevant disclosures. All statements are based on available information and are not an admission as to their accuracy or correctness.
The explosive adoption of video-enabled wireless mobile devices has caused an explosion of data traffic and exposed the capacity constraints of conventional wireless network topology.
Conventional wireless network (e.g. cellular network) deployment requires careful planning to maximize frequency reuse, minimize coverage dead zones and minimize inter-cell interference etc. The deployment is labour intensive due to significant amount of measurements and field trials. To reduce the cost of deployment, many network operators deploy macro cells which provide larger coverage footprint and higher capacity. This approach works when the subscribers' service types are mainly conversational (i.e. voice), interactive (e.g. web browsing, instant messaging etc.) or low rate streaming. These are the typical service types for 2G (e.g. GSM) and early 3G (e.g. UMTS Release 99 and CDMA2000) cellular networks where macro cell provides adequate quality of service to fulfill majority subscriber's needs.
More subscribers demand for faster data service as the bit rate at the air interface increases with the advance of the wireless technology (i.e. 3.5G and 4G). One instance of 3.5G is HSPA. One example of 4G networks is LTE (3GPP Release 8 and beyond), another is WiMax (IEEE802.16e and beyond). Given the limited available spectrum, the capacity becomes a serious issue for conventional macro cell. The capacity issue has caused a shift in cellular network deployment paradigm from well partitioned large coverage macro cells to densely deployed smaller cells (e.g. picocell and femtocell), many being added dynamically in non-fixed locations.
Today's SON (i.e. self configuration and provision) are not sufficient for densely deployed small cells to operate properly. SON capable of coordinating among neighboring cells on radio resource allocation is essential for densely deployed small cells to operate properly.
SUMMARY OF THE INVENTION
The present invention provides system architecture for a Self-organizing Network (SON) using Fractional Time Reuse (FTR) that can be applied, but not limited to, 3G/4G wireless cellular networks and beyond, as well as other wireless network.
In accordance with an aspect of the present invention there is provided a FTR SON system for optimizing the network performance (e.g. capacity, throughput, quality of service) by coordinating network elements in groups.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be further understood from the following detailed description with reference to the drawings in which:
FIG. 1 illustrates Fractional Time Reuse (FTR) SON for Two-Cell Case;
FIG. 2 illustrates FTR SON for Three-Cell Case;
FIG. 3 illustrates FTR SON for Three-Cell Covering the Entire Layer of Network;
FIG. 4 illustrates FTR SON for Multi-Layer Network, e.g., Pico-cells in Multi-floor Office Building;
FIG. 5 illustrates Network Procedures for FTR;
FIG. 6 illustrates UE procedures for FTR; and
FIG. 7 illustrates NoteB procedures for FTR.



DETAILED DESCRIPTION OF MODES OF PRACTICING THE DISCLOSURE
Referring to FIG. 1 there is illustrated a fractional time reuse self-organizing network (FTR SON) operating in two-cell configuration that uses embodiments of the present invention. The FTR SON 100 includes a first cell 102 and a second cell 104, which have an overlapping region 106. The first cell 102 includes a first node 108 (NodeB0) and a user equipment 110 (UE0) in the overlapping area 106. The first node 108 uses a first fractional time reuse schema 112 to connect to the user element 110 (UE0) when it is in the overlapping area 106. The second cell 104 includes a second node 114 (NodeB1) and a user equipment 116 (UE1) in the overlapping area 106. The second node 114 uses a second fractional time reuse schema 118 to connect to the user element 116 (UE1) in the overlapping area 106.
In operation, assuming NBi is the serving Downlink Shared Channel (DSCH) NodeB for UEi, i=0,1; where DSCH can be HS-DSCH for High Speed Packet Access (HSPA) or Physical Downlink Shared Channel (PDSCH) for Long Term Evolution (LTE). The FTR SON 100 puts long term scheduling restrictions onto the NodeB MAC scheduler such that the scheduling Time Transmission intervals (TTIs) (2 ms for HSPA, 1 ms for LTE) for UEs at the edge of the cells are staggered, e.g., in the two-cells case shown, UE0 110 is served on even numbering TTIs while UE1 116 is served on odd numbering TTIs. There is no restriction on the scheduling TTI timing for UEs 120 and 122 in the center of cells 102 and 104 respectively.
In the FTR SON 100, UEs can be classified as Center UEs, e.g. UE 120 and UE 122 or Edge UEs, e.g. UE 110 and UE 116 via Packet Data Protocol (PDP) context Quality of Service (QoS) requirement, Geometry (îor/Ioc), Channel Quality Indicator (CQI), Pilot Strength Measurement Message (PSMM, Pilot Ec/Io), or similar SINR measurements performed at the UEs and reported to the NodeBs 108 and 114.
In a typical HSPA deployment, at least 50% NodeB power is allocated to HS-PDSCHs, staggering scheduling TTIs can significantly reduce Ioc, therefore improve cell edge UEs performance. Similar performance improvement can be expected for LTE.
Referring to FIG. 2 there is illustrated FTR SON for three-cell case. This is the generalization of the two-cell case in FIG. 1, which is significant since the entire network layer can be covered by grouping cells in groups of three. The three-cell FTR SON 200 includes cells 202, 204 and 206. Each cell 202, 204 and 206 has a respective NodeB, NB0 210, NB1 212 and NB2 214 in communication with a respective user equipment UE, UE0 220, UE1 222 and UE2 224.
In operation, in the example shown in FIG. 2, each NBi is the serving Downlink Shared Channel (DSCH) NodeB for UEi, i=0, 1, 2. UE0 220 is interfered by NB1 212 and NB2 214, UE1 222 is interfered by NB2 214, UE2 224 is interfered by NB0 210. The FTR SON 200 puts a long term scheduling constrain onto NodeB MAC scheduler such that each UEi in service overlap areas 230, 232 and 234, is scheduled on TTIs numbered as 3n +i, respectively, i=0, 1, 2, shown as 240, 242 and 244 respectively.
By staggering the Transmission Time Interval (TTI) for UE0, UE1, UE2 intercell interference can be reduced considerably.
Referring to FIG. 3 there is illustrated the 3-cell grouping for covering an entire network layer with significantly reduced intercell interference at cell boundary. In the network 300, each cell 310 is divided into three sectors 320, 321 and 322, corresponding to I=0, 1, 2 as used in FIG. 2. Through this arrangement of Transmission Time Intervals (TTI) neighboring cells 310′ and 310′′ each use a different TTI from their adjacent neighbor.
Referring to FIG. 4 there is illustrated FTR SON for a multi-layer network. The FTR SON 400 of FIG. 4; can be used, for example for pico-cells in a multi-floor office building. The example FTR SON 400 shown includes four cells, 410, 420, 430 and 440 in two layers 450 and 460. Hence, the FTR SON 400 is in the form of 4n, 4n+1, 4n+2, and 4n+3 can be applied. In general, an FTR SON in the form of M*n, . . . , M*n+(M−1), where M in the Fractional Time Reuse Factor, is used when M cells are grouped together for optimization.
Referring to FIG. 5 there is illustrated network procedures for a FTR SON. The process of NodeB registration 500 begins with determining the topology of the neighbor group 510. The number of cells in the group determines the Fractional Time Reuse Fractor, M 520 and the NodeB time slot assignment M*n, . . . , M*n+(M−1) 530.
Referring to FIG. 6 there is illustrated UE procedures for an embodiment of FTR SON. Each UE periodically reports a Pilot Strength Measurement Message (PSMM) to determine a DSCH serving cell 600. Once the serving cell is determined, UE periodically reports 610 CQI to assist NodeB to determine UE's location (i.e, cell center vs cell edge).
Referring to FIG. 7 there is illustrated NodeB procedures for an embodiment of FTR SON. Each NodeB receives 700 a QoS requirement when a PDP context is configured/reconfigured for each individual UE and 710 a PSMM report from each individual UE via accessing 720 PSMM report from RRC API to determine DSCH serving cell per T-add network optimization parameter. After serving cell determination, NodeB receiving CQI report from individual UE via accessing 730 CQI report from MAC API. NodeB can compute the averaged CQI over a configurable time interval in combination of QoS requirement to determine each UE's location 740 (i.e., cell center vs cell edge). Finally, scheduling constrains to MAC scheduler is posted 750 via MAC API: unrestricted scheduling for UEs belonging to cell center category while restricted scheduling (FTR with specific time slot) for UEs belong to cell edge category.
Having now fully described the inventive subject matter, it will be appreciated by those skilled in the art that the same can be performed within a wide range of equivalent modifications, variations and adaptations without departing from the scope patent disclosure.
While this disclosure has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains and as may be applied to the essential features hereinbefore set forth.

## Claims

1. A method of configuring a self organizing wireless network (SON), the method comprising:
receiving a Quality of Service (QoS) requirement for each individual user equipment (UE) served by a wireless network node of a cellular network;
receiving a pilot strength measurement message (PSMM) from each UE;
determining downlink shared channel (DSCH) serving wireless node for each UE;
receiving channel quality indicator (CQI) for each UE;
computing average CQI value per each UE over a defined time interval in combination with QoS requirements to determine each UEs service category;
determining individual each UE's service category from the determined service category; and
posting scheduling constraints for the wireless nodes of the cellular network to a medium access control (MAC) scheduler, wherein posting the scheduling constraints further comprises:
assigning a first transmit time interval to a first wireless node;
assigning a second transmit time interval to a second wireless node different form the first transmit time interval; and
the first wireless node using the first transmit time interval for UE for mitigating interference from the second wireless node;
wherein the first and second transmit time intervals are assigned in dependence upon a fractional time reuse factor and node number, wherein the first and second time intervals are assigned based upon a formula M×n+i, where M is the fractional time reuse factor and n is the node number and i is a random number assigned from 0 to M−1.

2. The method of claim 1 wherein the scheduling constraints comprise posting unrestricted scheduling for UEs having a service category belonging to cell center category and restricted scheduling for UEs having a service category belonging to cell edge category.

3. The method of claim 1 wherein the QoS requirement is received when a Packet Data Protocol (PDP) context is configured or reconfigured.

4. The method of claim 1 wherein the using the first transmit time interval is for UE in a service coverage area overlapping with the second wireless node.

5. The method of claim 1 wherein using the first transmit time interval is for UE in a portion of its service coverage area adjacent to the second wireless node.

6. The method of claim 1, wherein each of wireless nodes are grouped together based on the overlapping coverage area identified by respective positive integers for optimization.

7. The method of claim 1 wherein determining the UE service category is in dependence upon at least one of QoS requirement, geometry, periodic PSMM and CQI reports.

8. The method of claim 1 wherein using the first transmit time interval is only for UEs classified as cell edge.

9. The method of claim 1 wherein the PSMM is provided from Radio Resource Control (RRC) Application program interface (API) to determine DSCH serving cell per T-add network optimization parameter.

10. The method of claim 1 wherein the scheduling constraints are posted to the MAC scheduler via MAC Application program interface (API).

11. The method of claim 1 wherein the unrestricted scheduling for UEs belong to cell center category while restricted scheduling (FTR with specific time slot) for UEs belong to cell edge category.

12. A non-transitory computer readable memory containing instructions for configuring a self organizing wireless network (SON), the instructions which when executed by a processor for performing:
receiving a Quality of Service (QoS) requirement for each individual user equipment (UE) served by a wireless network node of a cellular network;
receiving a pilot strength measurement message (PSMM) from each UE;
determining downlink shared channel (DSCH) serving wireless node for each UE;
receiving channel quality indicator (CQI) for each UE;
computing average CQI value per each UE over a defined time interval in combination with QoS requirements to determine each UEs service category;
determining individual each UE's service category from the determined service category; and
posting scheduling constraints for the wireless nodes of the cellular network to a medium access control (MAC) scheduler, wherein posting the scheduling constraints further comprises:
assigning a first transmit time interval to a first wireless node;
assigning a second transmit time interval to a second wireless node different form the first transmit time interval; and
the first wireless node using the first transmit time interval for UE for mitigating interference from the second wireless node;
wherein the first and second transmit time intervals are assigned in dependence upon a fractional time reuse factor and node number, wherein the first and second time intervals are assigned based upon a formula M×n+i, where M is the fractional time reuse factor and n is the node number and i is a random number assigned from 0 to M−1.

13. A system for configuring a self organizing wireless network (SON), comprising:
a component for receiving a Quality of Service (QoS) requirement for each individual user equipment (UE) served by a wireless network node of a cellular network;
a component for receiving a pilot strength measurement message (PSMM) from each UE;
determining downlink shared channel (DSCH) serving wireless node for each UE;
for receiving channel quality indicator (CQI) for each UE;
computing average CQI value per each UE over a defined time interval in combination with QoS requirements to determine each UEs service category;
determining individual each UE's service category from the determined service category; and
posting scheduling constraints for the wireless nodes of the cellular network to a medium access control (MAC) scheduler, wherein posting the scheduling constraints further comprises:
assigning a first transmit time interval to a first wireless node;
assigning a second transmit time interval to a second wireless node different form the first transmit time interval; and
the first wireless node using the first transmit time interval for UE for mitigating interference from the second wireless node;
wherein the first and second transmit time intervals are assigned in dependence upon a fractional time reuse factor and node number, wherein the first and second time intervals are assigned based upon a formula M×n+i, where M is the fractional time reuse factor and n is the node number and i is a random number assigned from 0 to M−1.