NETWORK ASSISTED USER ASSOCIATION AND OFFLOADING TECHNIQUES FOR INTEGRATED MULTI-RAT HETEROGENEOUS NETWORKS

• US 20140287743A1
• Filed: 05/30/2012
• Published: 09/25/2014
• Est. Priority Date: 01/23/2012
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Ali Yazdan Panah, Nageen Himayat, Shilpa Talwar, Shu-Ping Yeh
• Inventors: Yeh, Shu-Ping, Yazdan Panah, Ali, Himayat, Nageen, Talwar, Shilpa
• Granted Patent: US 9,119,120 B2
• Time in Patent Office: Days
• US Class Current: 455/426.1
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0096 Indication of changes in allocation
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/0066 of control information between different types of networks in order to establish a new radio link in the target network
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Methods and systems are described that incorporate joint network assisted offloading and cross-RAT (Radio Access Technology) user mapping techniques for integrated multi-RAT Het-Nets. Techniques are described for network based offloading and user association methods for multi-tier, multi-RAT HetNets, which account for overall user as well as network utility.

Claims

1. A macro base station (MBS) operating as an enhanced/evolved Node B (eNB) in an LTE network, comprising:

an air interface for communicating with users within a macrocell and connecting associated users to a core network;

processing circuitry configured to identify a number M of the weakest users associated with the MBS according to a defined strength metric, request a list of L preferred pico base stations (PBSs) for offloading from each of the weakest users, offload a weakest user to one of its L preferred PBSs if information received from that PBS indicates that the offloading would result in changes in an overall system utility and a user utility as defined by a specified utility metric that meet one or more specified criteria.

2. The MBS of claim 1 wherein the processing circuitry is configured to allow

users to initially associate with either the MBS or one of the PBSs as a function of the signal to interference and noise ratio (SINR) as measured by the users.

3. The MBS of claim 1 wherein the processing circuitry is configured such that the strength metric for identifying the weakest users is a function of the signal to interference and noise ratio (SINR) as reported by a particular user.

4. The MBS of claim 1 wherein the processing circuitry is configured to advertise a particular weakest user associated with the MBS to one of the user'"'"'s L preferred PBSs and receive from that PBS calculated pico system and user utilities that would result from that particular weakest user being offloaded to that PBS.

5. The MBS of claim 1 wherein the processing circuitry is configured to advertise the particular weakest user associated with the MBS to one of the user'"'"'s L preferred PBSs according to a rank ordering of the list of L preferred PBSs.

6. The MBS of claim 1 wherein the processing circuitry is configured to offload a weakest user to a particular one of its L preferred PBSs if the following conditions are met:

the offloading would result in an increase in the user utility of that weakest user by a specified minimum amount and the offloading would result in a degradation in an overall system utility by no more than a specified maximum amount.

7. The MBS of claim 1 wherein the processing circuitry is configured to calculate the overall system utility as the product of the pico system utilities.

8. The MBS of claim 1 wherein the processing circuitry is configured to evaluate the M identified weakest users for possible offloading in a rank order according to the strength metric and to discontinue evaluation of the weakest users if a particular user fails to meet the criteria for offloading.

9. A base station operating as an enhanced/evolved Node B (eNB) in an LTE network, comprising:

an LTE air interface for communicating with users within a cell served by the base station and connecting associated users to a core network;

a second air interface for communicating with users within the cell served by the base station and connecting associated users to a core network;

processing circuitry configured to calculate utilities for users being associated with the base station via either the LTE or second air interface based upon a selected utility metric and optimally partition users between the first and second air interfaces based on the calculated utilities.

10. The base station of claim 9 wherein the second air interface is a WiFi air interface.

11. The base station of claim 9 wherein the processing circuitry is configured to partition the users so as to maximize the selected utility metric by performing an exhaustive search across the number of partitions possible for the number of users associated with the base station.

12. The base station of claim 10 wherein:

the processing circuitry is configured to calculate the user utilities u^LTE and u^Wi-Fi for a user being associated with the base station via the LTE or Wi-Fi air interfaces, respectively, as;

u^LTE=G(R)R^LTE/K

u^Wi-Fi=G(K)R^Wi-Fi/K

where K is the number of users associated with the particular base station, G(K) is a function representing the multi-user diversity gain, and where R^LTE and R^Wi-Fi are measured or expected values of the data rates of the LTE and Wi-Fi air interfaces, respectively, given as;

R^LTE=B_LTE log(1+SINR_LTE)

R^Wi-Fi=B_Wi-Fi log(1+SINR_Wi-Fi)

where B_LTE and B_Wi-Fi are bandwidths and where SINR_LTE SINR_Wi-Fi are measured signal to interference and noise ratios of the LTE and Wi-Fi channels, respectively; and

,

the processing circuitry is configured to partition users between the LTE and Wi-Fi air interfaces in a manner that maximizes the calculated user utilities of the associated users.

13. The base station of claim 12 wherein:

the processing circuitry is configured to optimally partition its K associated users into m users associated via the Wi-Fi air interface and K-m users associated via the LTE air interface and to select the m users by;

(a) for each user, calculating R^LTE and R^Wi-Fi as measured or expected values of the data rates of the LTE and Wi-Fi air interfaces, respectively, and calculating a rate ratio R^LTE_i/R^Wi-Fi_i for each user i;

(b) rank ordering the K users according to their rate ratios in ascending order designated as users 1 through K where the first m users are assigned to the Wi-Fi air interface;

R^LTE₁/R^Wi-Fi₁<

. . . <

R^LTE_m/R^Wi-Fi_m<

. . . <

R^LTE_m+1/R^Wi-Fi_m+1<

. . . <

R^LTE_K/R^Wi-Fi_K

(c) selecting the number m such that;

(log(m)) (K−

m)/(log(K−

m)) (m)<

R^LTE_m+1/R^Wi-Fi_m+1

14. The base station of claim 10 wherein:

the base station is a pico base station (PBS) for serving a pico cell within a macro cell served by a macro base station (MBS); and

,

the processing circuitry is configured to;

receive an advertisement from the MBS for an identified particular weakest user associated with the MBS, calculate pico system and user utilities that would result from that particular weakest user being offloaded to the PBS and associated with the PBS via either the LTE or Wi-Fi interface after optimal partitioning of users, and report the calculated utilities to the MBS.

15. A method performed by a macro base station (MBS) operating as an enhanced/evolved Node B (eNB) in an LTE network, comprising:

allowing users to initially associate with either the MBS or a pico base station (PBS) operating within a macrocell served by the MBS as a function of the signal to interference and noise ratio (SINR) measured by the users;

identifying a number M of the weakest users associated with the MBS according to a defined strength metric; and

,

offloading a weakest user a PBS if information received from that PBS indicates that the offloading would result in changes in an overall system utility and a user utility as defined by a specified utility metric that meet one or more specified criteria.

16. The method of claim 15 further comprising requesting and receiving a list of L preferred PBSs for offloading from each of the weakest users.

17. The method of claim 16 further comprising advertising a particular weakest user associated with the MBS to one of the user'"'"'s L preferred PBSs and receive from that PBS calculated pico system and user utilities that would result from that particular weakest user being offloaded to that PBS.

18. The method of claim 17 further comprising advertising the particular weakest user associated with the MBS to one of the user'"'"'s L preferred PBSs according to a rank ordering of the list of L preferred PBSs.

19. The method of claim 17 further comprising calculating the overall system utility as the product of the pico system utilities.

20. The method of claim 15 further comprising evaluating the M identified weakest users for possible offloading in a rank order according to the strength metric and discontinuing evaluation of the weakest users if a particular user fails to meet the criteria for offloading.

21. A method performed by a pico base station (PBS) operating as an enhanced/evolved Node B (eNB) in an LTE network, comprising:

calculating utilities for users being associated with the base station via either an LTE air interface or a WiFi air interface based upon a selected utility metric; and

optimally partitioning users between the LTE and WiFi air interfaces based on the calculated utilities.

22. The method of claim 21 further comprising partitioning the users so as to maximize the selected utility metric by performing an exhaustive search across the number of partitions possible for the number of users associated with the PBS.

23. The method of claim 21 further comprising:

calculating the user utilities u^LTE and u^Wi-Fi for a user being associated with the base station via the LTE or Wi-Fi air interfaces, respectively, as;

u^LTE=G(K)R^LTE/K

u^Wi-Fi=G(K)R^Wi-Fi/K

where K is the number of users associated with the particular base station, G(K) is a function representing the multi-user diversity gain, and where R^LTE and R^Wi-Fi are measured or expected values of the data rates of the LTE and Wi-Fi air interfaces, respectively, given as;

R^LTE=B_LTE log(1+SINR_LTE)

R^Wi-Fi=B_Wi-Fi log(1+SINR_Wi-Fi)

where B_LTE and B_Wi-Fi are bandwidths and where SINR_LTE SINR_Wi-Fi are measured signal to interference and noise ratios of the LTE and Wi-Fi channels, respectively; and

,

partitioning users between the LTE and Wi-Fi air interfaces in a manner that maximizes the calculated user utilities of the associated users.

24. The method of claim 23 further comprising:

optimally partitioning its K associated users into m users associated via the Wi-Fi air interface and K-m users associated via the LTE air interface;

selecting the m users by;

(a) for each user, calculating R^LTE and R^Wi-Fi as measured or expected values of the data rates of the LTE and Wi-Fi air interfaces, respectively, and calculating a rate ratio R^LTE_i/R^Wi-Fi_i for each user i;

(b) rank ordering the K users according to their rate ratios in ascending order designated as users 1 through K where the first m users are assigned to the Wi-Fi air interface;

R^LTE_i/R^Wi-Fi₁<

. . . <

R^LTE_m/R^Wi-Fi_m<

. . . <

R^LTE_m+1/R^Wi-Fi_m+1<

. . . <

R^LTE_K/R^Wi-Fi_K

(c) selecting the number m such that;

(log(m)) (K−

m)/(log(K−

m)) (m)<

R^LTE_m+1/R^Wi-Fi_m+1

25. The method of claim 21 further comprising:

receiving an advertisement from the MBS for an identified particular weakest user associated with the MBS;

calculating pico system and user utilities that would result from that particular weakest user being offloaded to the PBS and associated with the PBS via either the LTE or Wi-Fi interface after optimal partitioning of users; and

,

reporting the calculated utilities to the MBS.