Coordinated AP for Tightly Coupled BS-AP Interworking for Multi-RAT Devices

IEEE 802.16ppc-10/0066

Project IEEE 802.16 Broadband Wireless Access Working Group

Title Coordinated AP for tightly coupled BS-AP interworking for Multi-RAT devices

Date 2010-11-02 Submitted

Source(s) Youngsoo Yuk, Eunjong Lee, Heejeong Cho and E-mail: [email protected], Inuk Jung [email protected], [email protected], LG Electronics [email protected]

Abstract Introduction of Coordinated AP for tightly coupled BS-AP interworking scenarios

Purpose To introduce the possible gain of enhanced AP in HN Multi0RAT scenarios This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It Notice represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, Release and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. The contributor is familiar with the IEEE-SA Patent Policy and Procedures: Patent and Policy . Further information is located at and .

1 IEEE 802.16ppc-10/0066 Coordinated AP for tightly coupled BS-AP interworking for Multi- RAT devices

Youngsoo Yuk, Eunjong Lee, Heejeong Cho and Inuk Jung LG Electronics Inc.

1 Introduction

The multi-RAT supporting device is being a key trend with the boom of smart phones. Especially cellular and WLAN interworking/switching can provide cheaper and more efficient wireless connection to the smart phone users. Even though SDR-based mobile terminal is one of the candidates for the next generation mobile terminal, dual-RAT devices becomes a dominant trend of wireless device for long time enough. In order to provide higher-level of experience to the customers with the dual-RAT devices, various interworking/co-operation models have been proposed. On the track of such an evolution, we are proposing a tightly coupled network model for dual-RAT operation.

2 WLAN and Cellular interworking Table 1 shows the comparisons of Pros/Cons of WLAN and cellular networks. The interworking may be going through the way choosing advantages relative to each other and making up the drawbacks with the modified operations.

Table 1. Pros/Cons of WLAN and Cellular systems WLAN Cellular Note Pros Higher BW Mobility Management WLAN provides Higher BW/Low Low cost for deployment Guaranteed QoS support latency Low overhead for maintaining Secure transmission Cellular provides QoS support connections Cellular provides Low access delay for random mobility/connection management access with small MSs Cellular co-ordinates the devices Cons Uncontrolled Mobility Higher access delay for to connect WLAN No connection management scheduled access Limited QoS support Large control overhead for data High power consumption for transmission network discovery Hard to managing interference

The basic approaches for enhancement are as follows:  In order to provide optimal data connection to the device under certain condition and service. i. More cost-effective, power-efficient RAT should be used for connections. ii. Ex) VoIP via cellular, Web via WLAN  Unified mobility/connection control via cellular network. i. Unified security association ii. WLAN mobility support iii. Unified QoS Management

2 IEEE 802.16ppc-10/0066 Various levels of inter-working architectures we can consider. In the current interworking architecture in WiMAX forum [2] and 3GPP [3], two independent networks are inter-connected via AAA proxy and/or various network layer functions. However only network layer interworking functions are considered in those architectures. If we consider the roaming between different networks, the model can be used as an efficient model. However many operators have both cellular and WLAN infra-structures and can provide both connectivity with a single subscription. Higher layer interworking has several limitations such as  The high power consumption for detecting WLAN AP without co-ordination  Higher signaling overhead comes from tunneling-based inter-working.  Large delays comes from higher layer interworking  Hard to support seamless mobility when the device is connected to WLAN.  In-device interferences between cellular and WLAN modules and loss from Co-Located Co- existence. If cellular BS can directly communicate with WLAN AP under its coverage, above challengeable issues can be resolved. Various enhanced equipments for wireless network can be considered for providing higher level of cooperation. Because the enhanced terminals have been proposed and discussed in various usage scenarios, and we focused on enhanced WLAN AP which provides higher level of interworking function to the mobile users.

A. Enhanced Terminal :  Terminal which has multi-access capability  It can connect to both BS and other WLAN devices  Scenarios : WLAN/Cellular Tethering (Relaying), Multi-RAT Client Co-operation

B. Enhanced AP  AP which has both WLAN/Cellular/Wired connecting capability  It is AP but has link to/from BS for control or data connection  Scenarios : WLAN router with Cellular Backhaul, integrated AP, Coordinated AP (WLAN AP with interworking connection with Cellular BS)

3 Enhanced AP

Wireless hotspots show the possible enhancements of scenarios how WLAN and cellular systems can help each other. In these scenarios, WLAN provides abundant connectivity from various wireless devices with higher BW while cellular system gives mobility to the devices.

Figure 1 shows the logical structure of Enhanced AP, and it can operate with 3 different modes and provides connectivity to/from devices with three different ways;

 Wireless Backhaul mode: WLAN connectivity to devices and cellular connection as a wireless backhaul  Converged gateway mode: Both WLAN and cellular connectivity to user devices, and wired IP backhaul  Coordinated AP mode: WLAN to user devices, cellular connection to/from BS for BS-AP coordination and wired IP backhaul.

3 IEEE 802.16ppc-10/0066

Enhanced AP WLAN GW

802.1X Core Standard Focus of multi-RAT

IEEE802.16 ABS

802.11 Data GLL Control Coordination Plane Plane Function AAA/ PDN 802.11 HA Control/ 802.11 RRM CS 802.16 802.16 PHY/MAC /IP PHY/ PHY/ MAC MAC

Figure 1. Structure of Enhanced AP

Enhanced AP: Wireless Backhaul

IEEE802.16 ABS

802.11 Data GLL Control Coordination Plane Plane Function AAA/ PDN 802.11 HA Control/ 802.11 RRM CS 802.16 802.16 PHY/MAC /IP PHY/ PHY/ MAC MAC

Enhanced AP : Converged Gateway P H 8 0 Y 2 / M . 1 A 1 C 8 G 0

2 Femto/WLAN AAA/ L

. PDN L 1 GW HA X 8 P M 0 H 2 A . Y C 1 / 6

4 IEEE 802.16ppc-10/0066

Enhanced AP : Coordinated AP

WLAN GW

IEEE802.16 ABS 802.11 Data GLL Control Coordination Plane Plane AAA/ Function PDN HA

802.11 Control/ 802.11 RRM CS 802.16 802.16 PHY/MAC /IP PHY/ PHY/ MAC MAC

Figure 2. Various operational modes of Enhanced AP

In this contribution, we focused on the last mode, “coordinated AP” and its possible gains.

4 The coordinated AP (C-AP)

Enhanced AP (E-AP) in the coordinated AP mode (call it as “C-AP” hereafter) which is for virtual carrier application can support various useful operations. In coordinated AP mode, a BS has controllability on the C- APs under its coverage. Even though the wired connection between BS and AP can be helpful to support a certain level of interworking, wireless link between BS and AP is able to provide more abundant functions for cooperation. The BS and C-APs may have communication channel to talk to each other.  The BS and C-APs can communicate for interworking.  The C-APs can communicate with each other via BS’s relaying and/or moderation.

The following co-operation scenarios we can expect with this system.

A. Sharing Access information C-AP may be possible to make a relation to its overlaid BS via IEEE802.16 wireless link. After turning on C-AP, it may start finding BS which it can communicate with, and register itself to the overlaid BS. From this interaction, BS can make a list of C-APs under its coverage without help of network operator. C-AP may be also provided the location information, neighbor information, radio configuration parameters and so on from the BS, and BS-assisted/controlled WLAN mobility can be implemented. From the information, BS can provide access information on WLAN AP to the dual-mode devices connected the BS. It can help reducing the device’s the power consumption for detecting WLAN APs. In addition, AP also can provide access information of cellular BS to the devices.

- BS’s Providing access information on C-APs to the devices  Low power consumption to detecting WLAN APs - C-AP’s providing access information on BS to the devices 5 IEEE 802.16ppc-10/0066  Fast BS-AP handover

B. Frame alignment for easy inter-working Wireless connection between BS and AP also make it possible to align their frame timing to mitigate self interference. If beacon signals broadcast by C-APs are aligned to BS’s DL subframe, no CLC mode is required for beacon reception in the devices. And, distributed beacon timing between C-APs can help detecting beacons with small searching duration for the devices. - Frame timing alignment/coordinating  Beacon signal can be aligned to the BS’s frame timing  Beacon signal can be distributed over multiple APs for co-ordination  Easy to scanning without CLC and scanning interval/unified timing reference  Easy to control the interworking based on timing relation

C. Inter-AP coordination Inter-AP Protocol (IAPP) and management function for multiple-AP environment can be supported by IEEE802.11f/v standard. Because that’s a semi-distributed protocol, the coordination may be partially optimized for not enough information on hidden nodes. In addition, neighbor AP may use different frequency channel, it’s hard to communicate with each other. A BS can be a hub for the communication, and it can be a centralized controller to coordinate all APs. With these communication links, BS can provide following flexibility to WLAN network. - Coordinated Dynamic Channel Switching - Coordinated Dynamic Adjustment of Transmission Power - Coordinated Dynamic Timing Adjustment - Coordinated Capacity Sharing among APs The coordinated managements may provide higher integrated network throughput [5]. In addition, with combining cellular off-loading, more optimized load balancing is possible and it yields more network throughput.

D. Integrated QoS/Connection management Even though the integrated security and IP flow mobility are already discussed and being standards, the level of cooperation is limited. Cellular and WLAN can share its security and context of an AMS, and it provides more easy way of interworking for QoS and connection management.

- QoS/Connection Management  Prioritized AMS scheduling  QoS provisioning for off-loading  Integrated Security Association  IP Flow mobility support

5 Conclusion Multi-tier network with cellular and WLAN is considered as an important solution for enhancing network capacity of wireless network. Interworking via radio interface between cellular BS and C-APs can provide abundant extension of management function to both the network service provider and the users. We proposed that IEEE802.16 WG should study of possible gains and feasibility of the introduction of C-AP.

6 IEEE 802.16ppc-10/0066 6 References [1] C802.16ppc-10/008r1, Study Report on Hierarchical Networks (Working document), Sept. 2010 [2] WiMAX Forum NWG, “Architecture, detailed Protocols and Procedures, WiFi – WiMAX Interworking,” , June, 2010 [3] TS23.234 V9.0.0 “3GPP system to Wireless Local Area Network (WLAN) interworking”, Sept. 2009. [4] Ramon Ferrus et al, “Interworking in Heterogeneous Wireless Networks: Comprehensive Framework and Future Trends,” IEEE Wireless Communication, April, 2010 [5] M.Abusuhaih et al, “AN Inter-Access Point Coordination Protocol for Dynamic Channel Selection in IEEE802.11 Wireless LANs,”pp17-24, ACNM’07, May, 2007 ======Proposed Text ======[remedy 1: Add following scenario as a section 2.2.6 in page 13]

2.2.6 BS-AP interworking by coordinated AP (C-AP)

In order to provide higher level of interworking function, cellular BS and WLAN AP may help each other through the wired and wireless connection. Hierarchical relations based on the coverage are defined between cellular BS and WLAN APs, and BS may provide configuration/co-ordination information to the WLAN APs in order to increase the interworking benefits. Coordinated AP (C-AP) is a WLAN AP which has wireless connectivity to BS A BS has controllability on the C-APs under its coverage. The BS and C-APs may have communication channel to talk to each other.  T h e BS and C-APs can communicate for interworking.  The C-APs can communicate with each other via BS ’ s relaying and/or moderation.

The following co-operation scenarios may be implemented with C-AP and BS interworking .

A. Sharing Access information In this scenario, C-AP can make a relation with its overlaid BS by itself. After turning on C-AP, it may start finding BS which it can communicate with, and register itself to the overlaid BS. From this interaction, BS can make a list of C-APs under its coverage without manual install/configuration. E-AP may be also provided the location information, neighbor information, radio configuration parameters and so on from BS, and BS-assisted/controlled WLAN mobility can be implemented. From the information, BS can provide access information on WLAN AP to the dual-mode devices connected the BS. It can help reducing the device ’ s the power consumption for detecting WLAN APs. In addition, AP also can provide access information of cellular BS to the devices.

- BS’ s Providing access information on C- AP to the devices  Low power consumption to detecting WLAN C-APs - C-AP ’ s providing access information on BS to the devices  Fast BS-AP handover

B. Frame alignment for easy inter-working W ireless connection between BS and C-AP also make it possible to align their frame timing to mitigate self interference. If beacon signals broadcast by C-APs are aligned to BS ’ s DL subframe, no CLC mode is required for beacon reception in the devices. 7 IEEE 802.16ppc-10/0066 And, distributed beacon timing between C-APs can help detecting beacons with small searching duration for the devices. - Frame timing Alignment/coordinating  Beacon signal can be aligned to the BS ’ s frame timing  Beacon signal can be distributed over multiple C-APs for co-ordination  Easy to scanning without CLC and scanning interval/unified timing reference

C. Inter-AP coordination Inter-AP Protocol (IAPP) and management function for multiple C-AP environment can be supported by IEEE802.11f/v standard. Because that ’ s a semi-distributed protocol, the coordination may be partially optimized for not enough information on hidden nodes. In addition, neighbor AP may use different frequency channel, it ’ s hard to communicate with each other. A BS can be a hub for the communication, and it can be a centralized controller to coordinate all APs. W ith these communication links, BS can provide following flexibility to WLAN network. - Coordinated Dynamic Channel Switching - Coordinated Dynamic Adjustment of Transmission Power - Coordinated Dynamic Timing Adjustment - Coordinated Capacity S h aring among APs The coordinated managements may provide higher integrated network throughput[] In addition, with combining cellular off-loading, more optimized load balancing is possible and it yields more network throughput.

D. Integrated QoS/Connection management Even though the integrated security and IP flow mobility are already discussed and being standards, the level of cooperation is limited. Cellular and WLAN can share its security and context of an AMS, and it provides more easy way of interworking for QoS and connection management.

- QoS/connection management  Prioritized AMS scheduling  QoS provisioning for off-loading  Integrated Security Association  IP F low mobility support

Wireless Wireless Connection Connection OTA Control OTA Control

WLAN WLAN Access Access Gateway Gateway WAG WAG

Packet Access Router

Access GW Access GW

Packet GGSN Access AAA Home AAA Home Router Server Agent Server Agent F igure X, wireless connection between BS and C-APs for coordinated operation.

8 IEEE 802.16ppc-10/0066 [remedy 2: Add following scenario as a section 2.2.6 in page 13]

4.2 Multi Radio Access Technology [R-X] I EEE 802.16 BS shall be able to communicate with IEEE 802.11 AP under its coverage via wired and/or wireless connection for interworking operation. IEEE802.16 BS should be able to configure and control the operation and configuration of the IEEE802.11 APs under its coverage.

======End of proposed text ======