This document proposes using WLAN for proximity-based service (ProSe) discovery and communication in beyond 4G (B4G) networks as a simpler approach than adapting the LTE physical layer. It describes using an integrated E-UTRAN and WLAN architecture where WLAN serves as the direct communication path between user equipment for ProSe. The main advantages are faster time-to-market and utilizing unlicensed spectrums for ProSe in B4G networks. It also summarizes several ProSe use cases and existing ProSe technologies.

1. Proximity-based Service Beyond 4G Network :
Peer-aware discovery and communications using
E-UTRAN and WLAN
Shiann-Tsong Sheu∗§, Yi-Hsueh Tsai†¶, Yi-Ting Lin†, Kan-Chei Loa†,
Tsing-Yu Tsai†‡, Chun-Che Chien†‡, and Dun-Cheih Huang∗
∗Dept. Communication Engineering, National Central University, Taoyuan, Taiwan
†Institute for Information Industry, Taipei, Taiwan
‡Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan
Email: stsheu@ce.ncu.edu.tw§, lucas@iii.org.tw¶
Abstract—The arising Proximity-based applications and ser-
vices represent a recent and enormous socio-technological trend
that has been generating innovative business models for the
mobile networks. This paper proposes a WLAN-based B4G
network architecture for Proximity-based Service (ProSe) where
WLAN serves as the direct communication path between user
equipment. The peer-aware discovery and communication are
supported by an integrated E-UTRAN (LTE radio plus core
networks) and WLAN. The main advantages are faster time-to-
market and utilizing unlicensed spectrums for Proximity-based
Services in beyond 4G network.
Index Terms—proximity-based service, beyond 4G, device-to-
device communication, service discovery, LTE, WLAN
I. INTRODUCTION
The arising ProSe applications and services represent a
recent and enormous socio-technological trend that has been
generating innovative business models for the mobile net-
works. The purpose of these applications is to discover in-
stances of the applications running in devices within proximity
of each other, and ultimately exchange application-related
information. Currently in 3G/4G networks, ProSe has been
realized in a limited scope and functionalities through Over
The Top (OTT) applications, e.g. Foursquare, Facebook, and
other OTT applications. These applications enable ProSe with
centralized servers combining with the location information
supplied by Global Positioning System (GPS). However, GPS
is not reliable in the indoor environment. Moreover, the OTT
approach with centralized servers incurs undesired network
overheads and latency for discovery and communication ser-
vices. In short, the drawbacks of the OTT approach are un-
scalable when the density of user equipment (UE) is high,
unreliable when a user is indoor or requires low delay services,
and un-sustainable for the operator that cannot control or build
a business model to share the revenue from OTT providers.
Long-Term Evolution (LTE), specified by 3rd Generation
Partnership Project (3GPP) standard organization, has been se-
lected as the technology for the 4G networks by vast majority
of commercial wide area network (WAN) operators and public
safety communities. However, current 3GPP LTE Release
10/11 specifications are only partially suitable for advanced
ProSe applications and services for commercial and public
safety usages, because all such traffic and signaling would
have to be routed through the radio and core networks. Thus
it impacts their performance and adds unnecessary load to the
network while performing ProSe services. These limitations
must be lifted in future LTE releases such that more advanced
proximity-based applications could be enabled in beyond 4G
(B4G) network. The general approach of resolution is to
introduce direct device-to-device (D2D) communication into
LTE, where all ProSe traffic would take the shortest path
between two users.
The existing LTE-based ProSe discovery and communi-
cation would require fundamental adaptation of the LTE
physical layer and radio. As compared with the LTE-based
ProSe, this paper proposes a simpler approach that requires
fewer adaptations at higher layers to quickly enable ProSe
by using interworking architecture between Wireless Local
Area Network (WLAN) and E-UTRAN (LTE radio plus core
networks), where the WLAN is served for ProSe discovery
and communication.
The rest of this paper is organized as follows. First,
Section II characterizes ProSe by several use cases, whilst
Section III and IV depict current ProSe standard activities and
existing technologies. Section V and VI illustrates proposed
architecture in details with reference models and sequence
charts. Finally, Section VII provides conclusions and potential
research directions.
II. PROXIMITY-BASED SERVICE USE CASES
ProSe discovery and ProSe communication are two key
technologies of the proximity-based services. Compared to
the existing server-based location positioning on the 3G/4G
networks, ProSe discovery directly seeks interesting targets
in proximity without any location information. Similarly,
ProSe communication provides a new service whose path is
established between the UEs or via local routing through the
base station without traversing the backhaul link and the core
network. In general, ProSe could be best characterized by the
following service scenarios and related business models.

2. A. Restricted Discovery
Restricted discovery use case [1] describes a basic scenario
for ProSe discovery. For restricted discovery, the ProSe dis-
covery only operates with explicit permission from the UEs
being discovered. A social networking application subscriber
uses a ProSe-enabled UE to find his friends in proximity.
For instance, Mary and John are friends, John and Peter are
friends, but Mary and Peter are not friends. Mary, John, and
Peter subscribe to a given social networking application that
has a proximity-based discovery feature. As Mary’s UE comes
into proximity of John’s and Peter’s UEs, Mary’s UE and
John’s UE mutually detect each other in proximity. However,
Mary’s UE and Peter’s UE do not detect each other though in
proximity because they do not permit a UE to be discoverable
by unrelated subscribers. After the restricted ProSe discovery,
Mary could perform regular social-networking activities, e.g.
transferring data or sharing photos, with John via the social
networking application. Note that in order to allow Mary, John,
and Peter directly discovering each other while their network
service subscriptions might belong to different operators, a
common operating frequency band among different operators
for the proximity-based discovery services are required.
B. Open Discovery
Open discovery use case [1] describes a case in which an UE
discovers another UE without permission by the discoverable
UE. A local advertisement scenario [6], where a subscriber
uses ProSe-enabled UE to find points of interest (POI), is used
to illustrate the open discovery.
Assume Mary carries her ProSe-enabled UE and stores
of 7-Eleven, Starbucks, and McCafe equipped with ProSe-
enabled UEs with a local advertisement application, which
permits being discovered by any UEs. As Mary walks into the
neighbourhood of a 7-Eleven store, Mary’s UE discovers the
UE of 7-Eleven. Hence Mary is notified of the proximity of the
7-Eleven. Mary then decides to look for a coffee shop, and thus
following interaction with her application, Mary is notified of
the proximity of a Starbucks, whose UE was discovered by
Mary’s UE. Note that during the discovery process, Mary is
not notified of the proximity of other establishments not found
of interest to her.
Generally, after discovery, Mary’s UE should reveal its
identity to the UE of the store in order to establish a ProSe
communication session with the UE of the store for retrieving
further advertised information (texts, coupons, pictures, video
clips, and other information). One way to address this privacy
concern of revealing user’s identification is to smartly combine
anonymous discovery with the digital signage in the local
advertisement setup depicted below.
Assume that a digital signage in the neighborhood is used to
display advertisements of the 7-Eleven, Starbucks and McCafe
and is equipped with a ProSe-enabled UE. As Mary walks
into the viewing range of the digital signage, the digital
signage is notified of the event that an anonymous user, who
had discovered the Starbucks, is within its proximity. The
ProSe-enabled UE of the digital signage interactively displays
the Starbucks’ related information to Mary without knowing
the identity of Mary’s UE. In this case, Mary anonymously
found all related information of her preferred coffee shop on
the digital signage with only light-weighted ProSe discovery
signals without invoking any ProSe communications at all.
In practice, the open discovery could create a new business
model of value-added services where the operator is able to
receive local advertisement revenues from the store owners,
who could use these ProSe services for free. A ”free” ProSe
service would further motivate more users to use the local
advertisement service that in turn generates more revenues for
the operator.
C. Service Continuity
This use case depicts service continuity between the net-
work infrastructure and the direct communication path. In this
use case, ProSe discovery and communication are used to
seamlessly offload traffic from the infrastructure network when
two UEs are within proximity.
Assume Mary and Peter use ProSe-enabled UEs and they
are engaged in a data session that is being routed over the
operator’s core network infrastructure. As Peter moves within
proximity of Mary, Peter and Mary’s UEs discover each
other and the data session is switched to a proximity-based
communication path between them. When Peter moves out of
the proximity of Mary, the data session is switched back to
the infrastructure path. Importantly, the switching of the data
session would not perceived by the users at all.
III. PROXIMITY-BASED SERVICE IN 3GPP AND
IEEE
3GPP and Institute of Electrical and Electronics Engineers
(IEEE) are currently in the process of studying Proximity-
based Service.
A. 3GPP
3G/4G WANs, the 3GPP dominating technologies, have vast
opportunity to promote future and more advanced proximity-
based applications by becoming the platform to enable
proximity-based discovery and communication between de-
vices. The feasibility study item of ProSe has been created
in 3GPP Technical Specification Group (TSG) Service and
System Aspects Working Group 1 (SA1) since 2011, where
use cases and service requirements are being studied, includ-
ing network operator control, authentication, authorization,
accounting, and regulatory aspects [1].
The objectives of this study item are to study use cases
and identify potential requirements for an operator network
which devices are in proximity under continuous controlled
3GPP networks coverage. The scopes of the study include
commercial/social use, network offloading, public safety, and
integration of current infrastructure services to assure the
consistency of the user experience including reachability and
mobility aspects.
The ProSe study in SA1 is scheduled to be completed by
the end of 2012. It is expected that studies on ProSe solutions

3. in RAN (radio access) and SA (network architecture) will start
in 2013 following LTE release 12 schedule.
B. IEEE
Infrastructure Service Discovery (ISD) Study Group [7] is
created within the IEEE 802.11 working group to address the
problem of how a station, e.g., a mobile device, discovers
the availability of services within the network from another
station, e.g., the associated Access Point (AP). During the
meeting held in May 2012, the ISD SG concludes to schedule
the PAR for review and vote in July 2012.
IV. EXSTING PROXIMITY-BASED SERVICE
TECHNOLOGIES
A. WLAN
The IEEE 802.11 standard supports two operating modes,
the infrastructure mode and ad-hoc mode. The former provides
users the Internet connections and the latter is a simple method
for wireless devices to directly communicate with each other
without the assistance from AP. Currently, the Wi-Fi Alliance
has developed a new specification, called the Wi-Fi Direct or
Wi-Fi Peer-to-Peer (P2P) [8], for directing Wi-Fi connections
between client devices which may have associated with AP(s).
However, the 802.11 STAs adopting ad-hoc mode and P2P
mode still rely on the active scan procedure to retrieve the
Layer-2 neighborhood information, including the service set
ID (SSID), basic service set capability, security suites, and
other information. Lacking the precise ProSe information
would force a station to establish Layer-2 connection with
every neighbor in order to determine whether there is any
desired ProSe service provided in the peer device. How to
quickly enable the ProSe service over WiFi P2P networks is
still an open and interesting issue.
B. Bluetooth
A specific service discovery protocol (SDP) is needed in the
Bluetooth environment, as the set of available services would
change dynamically due to the RF proximity of devices in
motion. More specifically, such SDP provides a means for
applications to discover which services are available and to
determine the characteristics of those available services. The
major problem with Bluetooth SDP is that every SDP client
must first establish an L2CAP connection and then an SDP
connection with SDP server before attempting to discover a
designated service. If both SDP client and server are slaves in
a piconet, the client has to form a new piconet and act as a
master of this piconet for inviting the server to be the slave
of this piconet. Such burden procedure definitely impacts the
user experience.
C. FlashLinQ
FlashLinQ [2]-[3] is a proprietary Qualcomm technology
using synchronous OFDM-based physical layer for direct D2D
communication that supports device discovery over a 1 km
range and can discover a few thousands devices within 8 sec-
onds. FlashLinQ exploits existing cellular network as a global
WLAN 3GPP IP Access
3GPP Home Network
WLAN Access Network
WLAN
UE
Ww
HSS HLR
Offline
Charging
System
OCSWa
Wn
Wx
D' / G
r'
Wf
Wo
Wi
Intranet / Internet
Wm
WAG Wp PDG
Wg
Wu
Dw
SLF
3GPP AAA
Server
Wy
Wz
Fig. 1. 3GPP/WLAN interworking reference model [4].
timing synchronization sources. Each mobile device advertises
its presence and discovers other D2D devices autonomously
and continuously without any group owner. Single carrier
based discovery signal in FlashLinQ prolongs discovery range
and standby time. A key feature of the D2D communication
in FlashLinQ is the cross-layer PHY/MAC mechanism that
utilizes analog signaling to enable distributed channel-aware
spatial resource allocation and scheduling through analog
signaling. FlashLinQ could coexist and share the resource
with an existing cellular network. Therefore, the operation
of FlashLinQ requires licensed spectrum allocation by the
network operator.
V. PEER-AWARE DISCOVERY AND
COMMUNICATIONS USING E-UTRAN AND WLAN
TECHNOLOGIES
Albeit 3GPP ProSe enables LTE subscribers to discover
and communicate with other subscribers in proximity under
continuous operator network control, there is no restriction on
the radio access technology used for the data plane of the
direct communication. Therefore, ProSe could conceivably be
implemented by integrating WLAN with the 3GPP system,
where the 3GPP system is used for network control and the
WLAN is used for data exchange.
Enabling WLAN for ProSe in 3GPP systems can
be achieved by adding ProSe functionalities to existing
LTE/WLAN interworking mechanisms (I-WLAN), which have
been defined in 3GPP specifications in Release 6. Even though
the communication between UEs is traversing through WLAN,
the control is not taken away from the operator. Actually
this scheme extends the operator’s control by placing the
WLAN connections of the UE under the operator’s man-
agement for D2D services, which effectively expands the
operator’s network and, consequently, improves the operator’s
service capabilities and diversity. Access Network Discovery
and Selection Function (ANDSF) facilitates a UE to choose
the best access network that in turn assists the operator to
manage network resources without losing the ability to control
and charge for wireless access through WLAN. Proximity-
based discovery and direct communication over WLAN is
particularly well suited to offload ProSe traffic, since it allows
a 3GPP operator to divert traffic and interference from the
3GPP radio access network. The distinct features of using
WLAN for direct mode in ProSe are:
• utilizing unlicensed spectrum for direct communication,

4. WLAN
UE
WLAN
AN
TE
End-to-End Service
WLAN Bearer Service External Bearer Service
Fig. 2. QoS Architecture for WLAN Direct IP Access [4].
• designating a common WLAN spectrum for UEs camped
on different Public Land Mobile Networks (PLMNs).
A. Basic interworking reference model and direct IP access
In 3GPP TS 23.234 [4], it specifies system description for
interworking between 3GPP systems and WLANs. The intent
of 3GPP/WLAN interworking is to extend the 3GPP services
and functionality to the WLAN access environments. The
3GPP/WLAN interworking System provides bearer services
allowing a 3GPP subscriber to access 3GPP packet switch
(PS) based services with WLANs. The basic 3GPP and WLAN
interworking reference model is shown in Fig. 1. Fig. 2 shows
the QoS architecture of WLAN Direct IP Access defined in
3GPP TS 23.234. The End-to-End Service provides transport
of the signaling and user data between the WLAN UE and
another (external) terminal equipment (TE) or correspondent
node passed over different bearer services of the network.
B. E-UTRAN/WLAN interworking reference model
According to 3GPP TS 22.234 [5], the 3GPP system shall
support WLAN UE concurrent connections to both WLAN
and 3GPP system. Based on the 3GPP-WLAN interworking
reference model in Fig. 1, the proposed reference model for
two WLAN UEs simultaneously connecting to both WLAN
and E-UTRAN is illustrated in Fig. 3, where the direct
communication between two WLAN UEs can be realized by
WLAN Direct IP Access, as shown in Fig. 2, through the
WLAN access network (i.e., the Ww interface).
C. Scenario for E-UTRAN and WLAN interworking
A scenario regarding ProSe using E-UTRAN and WLAN
interworking demonstrates the operator’s control over E-
UTRAN and WLAN interworking is addressed as follows.
While walking down the street, Sam’s ProSe-enabled UE is
aware of point of interest (POI) in proximity by proactively
detecting or being informed by the 3GPP network. Sam has
previously specified his preferences in his configuration. Thus,
he continuously receives announcements, advertisements and
special offers, matching his preference, in various media
formats via the E-UTRAN or WLAN. As Sam moves, POIs
continuously move in and out of WLAN range of his UE.
While being nomadic, Sam’s UE communicates with an
enhanced ANDSF to dynamically discover and select an
optimized WLAN network for ProSe based on operator policy
and his UE profile. As Sam’s POIs move in and out of WLAN
range, the operator maintains the continuity and QoS of Sam’s
sessions by monitoring the sessions via periodic updates from
WLAN
access
network
WLAN
UE
eNB
SG
PDG
PCRF
Operator IP
ServicesMME
HSS
S1u
S5
S7
LTE-Ub
S1-MME
S6a
Rx+
SGi
S11
LTE-Ub
SGi
WLAN
UE
WAG
3GPP
AAA
Server
Wn
Sp
OCS
Intranet / Internet
Wy
Wo
Wg
Wm
Wa
Wx
SLF HLR
Dw D'/Gr'
Offline
Charging
System
Wf
Wz
Wu
WwWw
Wu
Fig. 3. E-UTRAN/WLAN interworking reference model.
the UEs and by moving the sessions back to the E-UTRAN
when/if the performance falls below some acceptable level.
Since each access network connection, E-UTRAN or WLAN,
is authorized by the operator’s evolved packet core (EPC),
ProSe via WLAN is charged by the operator accordingly.
VI. PROXIMITY-BASED PEER-AWARE DISCOVERY
AND COMMUNICATION VIA WLAN
Scenario 1: ProSe Discovery via two WLAN APs
Based on Figure 3, the reference model for two WLAN UEs
perform ProSe via two WLAN APs is shown in Fig. 4.
The following procedure is proposed to perform proximity-
based discovery piggyback on legacy WLAN registration pro-
cedure to the Authorization, Authentication, and Accounting
(AAA) server.
1) The ProSe-enabled application registers to the ProSe
module of the WLAN UE.
2) The ProSe module of the WLAN UE registers to the
ProSe AAA via a WLAN AP.
3) The WLAN AP is notified the ProSe capability infor-
mation of the WLAN UE from the ProSe AAA server.
4) The WLAN UE sends the application information of the
user to the WLAN AP.
5) The WLAN AP updates the application information of
the user to other WLAN AP(s) in proximity via inter-AP
protocol (IAPP).
6) The WLAN AP updates the neighbor WLAN UE’s (e.g.
matched WLAN UE) application information of the user
to the WLAN UE.
7) The WLAN UE notifies the applications the list of users
who are in proximity.
Moreover, in Fig. 4, GLMC (Gateway Mobile Location
Centre) requests routing information from HLR and HSS to
support LCS (LoCation Service). LEMF (Law Enforcement
Monitoring Facility) and DF2 (Delivery Function 2) support
operators to perform lawful interception for WLAN peer-to-
peer communication.
An example of the sequence chart is shown in Fig. 5 where
the detailed descriptions are given as follows.

5. OCS
Wo
WAG
Wn
Internet
Wa
Offline
Charging
System
Wf
Wn Wa
WLAN AN
3GPP AAA
Server
Wg
User#1 APP User#2 APP
WLAN UE#1 WLAN UE#2
ProSe Module ProSe Module
Ww Ww
ProSe AAA
WLAN AP#2
ProSe FB#2
WLAN AP#1
ProSe FB#1
ProSe CB
ProSe
Server
Wp2p
GMLC
La
LRF
ProSe Centre
DF2
LEMF
Fig. 4. ProSe discovery via WLAN APs.
Assume that Mary and Peter have carried ProSe-enabled
UEs with WLAN capability and subscribed to the same
operator with ProSe. As soon as the WLAN AP connects
to the 3GPP network, the ProSe function block (FB) in
WLAN AP registers to the ProSe AAA server. When user,
e.g., Mary or Peter, starts a proximity-based application, the
application first registers to the ProSe module in user’s UE,
and then the ProSe module confirms the registration. Upon
user’s WLAN UE detecting a WLAN AP, the WLAN UE
connects to network via the WLAN AP. Afterward, user’s
UE registers to 3GPP AAA server via WLAN AP, and the
ProSe module in user’s UE also registers to the ProSe AAA
server at the same time. The ProSe AAA server sends back
the ProSe capability information of user’s WLAN UE to the
ProSe FB in the associated WLAN AP. Furthermore, the ProSe
FB in WLAN AP requests the WLAN UE for application
information of the user such as user friend list, and then
the ProSe module in user’s WLAN UE sends those to the
WLAN AP. Afterward, the ProSe FB in WLAN AP updates
the application information of the user to other WLAN AP(s)
in proximity. As Mary’s and Peter’s ProSe-enabled WLAN
UEs have completed the above procedure, the ProSe FBs in the
corresponding WLAN APs are aware of that Mary and Peter
are associated. Then the ProSe FBs in corresponding WLAN
APs send the ProSe information to the Mary’s UE and Peter’s
UE, respectively. After receiving the ProSe information, the
ProSe module in user’s WLAN UE notifies the user that his/her
friend(s) is in proximity. Furthermore, instead of sending the
ProSe information to Mary’s and Peter’s UEs directly, the
ProSe FBs in corresponding WLAN APs can request those
WLAN UEs to scan neighbors directly via WLAN peer-to-
peer discovery. The sequence chart of WLAN peer-to-peer
discovery is shown in Fig. 6.
Scenario 2: ProSe Discovery via WLAN Group Owner
In addition to ProSe discovery via WLAN APs, ProSe
discovery can be perform through WLAN peer-to-peer dis-
covery, where WLAN AP operates as a WLAN peer-to-peer
Same procedures between WLAN UE#2, WLAN AP#2 and AAA Server
Peter s
APP Peter s UE
Register to
P2P Module
turn on
Confirm
ProSe Module
WLAN AP#1
ProSe FB#1
3GPP AAA
Server
WAG
turn on
Register to ProSe AAA
Confirm
Register to 3GPP AAA Server
Send information of Mary s UE To ProSe FB#1
Mary s
APP Mary s UE
Register to
P2P Module
turn on
Confirm
ProSe Module
Confirm
Confirm
Connected to WLAN AP
WLAN AP Synchronization & Indication
Register to ProSe AAA
Confirm
Mary and Peter are relatedMary s UE is detected
Peter s UE is detected
Peter s UE
is detected
Mary s UE
is detected
ProSe AAA
WLAN AP#2
ProSe FB#2
turn on Register to ProSe AAA
Confirm
Update Mary s
Info. to FB#2
Request for Mary s information
Mary s information
Mary and Peter are related
Fig. 5. Sequence chart of WLAN AP-assisted discovery.
Peter s
APP Peter s UE
ProSe Module
WLAN AP#1
ProSe FB#1
Mary s
APP Mary s UE
ProSe Module
Request to scan neighbor
(search for Mary s UE)
Request to scan neighbor
(search for Peter s UE)
Peter s UE
is detected
Mary s UE
is detected
WLAN AP#2
ProSe FB#2
Update Mary s
Info. to FB#2
Update Peter s
Info. to FB#1
Same procedures for WLAN peer-to-peer discovery
Mary and Peter are related
Fig. 6. Sequence chart of WLAN peer-to-peer discovery.
group owner [8]. The following procedure is proposed to
perform proximity-based discovery via WLAN peer-to-peer
technology shown in Fig. 7, where the ProSe server provides
Proximity-based service and controls the signaling, including
ProSe discovery, network communication selection, network
security, and other service and controls.
1) The ProSe-enabled application registers to the ProSe
module of the WLAN UE.
2) The WLAN UE joins the WLAN peer-to-peer group
established by WLAN AP as a WLAN GO (WLAN
group owner).
3) WLAN GO exchanges member information to every
WLAN UE, and the WLAN UEs detect all together in
proximity.
4) The ProSe modules of WLAN UEs register to ProSe
AAA server via WLAN GO.
5) The AAA server sends WLAN UEs’ information to
ProSe server.
6) ProSe server requests for WLAN UEs’ information from
WLAN UEs.
An example of the sequence chart is shown in Fig. 8 where
the detailed descriptions are given as follows.
Assume that Mary and Peter have carried ProSe-enabled
UEs with WLAN peer-to-peer capability under a WLAN AP
acting as a WLAN peer-to-peer group owner. As soon as the
WLAN GO connects to the 3GPP networks, the ProSe FB if

6. WAG
User#1 APP
ProSe Module
WLAN UE#1
User#2 APP
ProSe Module
WLAN UE#2
ProSe AAA
3GPPAAA
Server
OCS
Offline
Charging
System
ProSe
Server
LEMF
DF2
Internet
Wn
Wp2p
Wg
Wo
Wf
ProSe Module
WLAN GO
P2P Module
Wp2p Wp2p
WLAN AP as
WLAN GO
Wa
Fig. 7. ProSe discovery via WLAN AP as group owner with ProSe server.
the WLAN GO registers to the ProSe AAA server. After syn-
chronizing with WLAN UEs, users’ UEs join the WLAN GO.
Through periodical synchronization, the WLAN GO updates
Mary’s and Peter’s member information to Peter and Mary,
respectively. After completing the procedure above, Mary’s
and Peter’s UEs detect each other in proximity, enabling
to perform WLAN peer-to-peer communication. Afterward,
users’ UEs register to 3GPP AAA server, and the ProSe
modules of UEs register to ProSe AAA server. The ProSe
AAA server then sends users’ UEs information to ProSe
server. Finally, the ProSe server requests UEs to send APP’s
information, and the ProSe modules of UEs response with
APP’s information and geometry location information of the
UEs to ProSe server.
Moreover, the Mary’s and Peter’s UEs can also be detected
by other ProSe-enabled UEs via both WLAN peer-to-peer
discovery and WLAN AP assisted discovery.
VII. CONCLUSIONS
The emerging LTE-based proximity-based service (ProSe)
discovery and communications would require fundamental
adaptation of the LTE physical layer (PHY) and radio. Taking
standardized procedure in 3GPP to make major change in PHY
and radio will normally take several years to complete. As a
consequence, the products will take another several years to be
available in the market, and more time on top of that to ensure
a large enough device population for any LTE-based ProSe
to be viable. Nowadays, WLAN-based offload solutions are
already embedded in smart phones and supported by 3G/4G
networks. As compared with the LTE-based ProSe, this paper
proposes a simpler approach that only requires few adaptations
at higher layers to quickly enable ProSe via standardized
3GPP/WLAN interworking solution. The faster time-to-market
envisioned solution will provide operators a chance to capture
a portion of the Over The Top (OTT) proximity service market
much earlier than an LTE-based ProSe solution. The proposed
scheme also allows network operators that do not have licensed
spectrum allocated for ProSe usage to deploy ProSe.
turn on
Same procedures between Peter's UE, WLAN GO, AAA Server & ProSe Server
Mary's
APP Mary's UE
ProSe Module
Peter's
APP Peter's UE
ProSe Module
WAG 3GPPAAA
Server
ProSe AAA
Register to
P2P Module
Confirm
Register to ProSe AAA
Register to 3GPPAAA Server
Register to ProSe AAA via WLAN GO
Confirm
Confirm
Mary's & Peter's UE can be detected by other ProSe-enabled UEs
WLAN GO
ProSe FB
P2P Module ProSe
Server
Register to ProSe Server
Confirm
Register to
P2P Module
Confirm
Synch. & WLAN GO Info.
turn on
Synch. & WLAN GO Info.turn on
Notify WLAN
GO detected
Notify WLAN
GO detected
Join WLAN GO
Send Mary's Info.
Join WLAN GO
Send Peter's Info.
Synch. & WLAN GO Info.
Synch. & WLAN GO Info.
t0
Update Peter's member Info.
Update Mary's member Info.
Notify Peter's UE
& Peter detected
Notify Mary's UE
& Mary detected
Confirm
Confirm
Send Mary's Info.
Request for Mary's Info.
Send Mary's Info.
to ProSe Server
Fig. 8. Sequence chart of ProSe discovery via WLAN GO with ProSe server.
Finally, WLAN-based ProSe solution is a fertilized ground
for innovations. Challenges for beyond 4G ProSe evolutions
might include, but not limited to, low-power-always-on ProSe
discovery, WLAN and LTE radio integrations, New Carrier
Type (NCT) of LTE for direct communication, and non-
orthogonal radio design for high performance ProSe.
ACKNOWLEDGEMENT
The authors of this paper would like to thanks participants of
3GPP SA1 FS ProSe for their constructive inputs and debates
on ProSe use cases and requirements.
REFERENCES
[1] 3GPP TR 22.803 V0.3.0 “Feasibility Study for Proximity Services
(ProSe) (Release 12),” May. 2012.
[2] M. S. Corson, J. Li, V. Park, T. Richardson and G. Tsirtsis, “Toward
Proximity Aware Internetworking,” IEEE Wireless Communications, pp.
26-33, Dec. 2010.
[3] F. Baccelli, N. Khude, R. Laroia, J. Li, T. Ricahrdson, S. Shakkottai,
S. Tavildar, X. Wu, “On the design of device-to-device autonomous
discovery,” 10.1109/COMSNETS.2012.6151335, pp. 1-9, Dec. 2012.
[4] 3GPP TS 23.234 V10.0.0 “3GPP system to Wireless Local Area
Network (WLAN) interworking; System description (Release 10),” Mar.
2011.
[5] 3GPP TS 22.234 V10.0.0 “Requirements on 3GPP system to Wireless
Local Area Network,” Sep. 2012.
[6] 3GPP SA1 No.58 S1-121152 “Enhanced Open Discovery Use Case,”
Jun. 2012.
[7] http://www.ieee802.org/11/Reports/isd update.htm
[8] WF-P2P1.1 “Wi-Fi Peer-to-Peer (P2P) Technical Specification Version
1.1,” Mar. 2011.