OpenAirInterface 4G: an open LTE network in a PC
Navid Nikaein, Raymond Knopp, Florian Kaltenberger, Lionel Gauthier,
Christian Bonnet, Dominique Nussbaum, and Riadh Ghaddab
Eurecom
06410 Biot Sophia-Antipolis, France
nikaeinn,knopp,bonnet,kaltenberger,gauthier,nussbaum,ghaddab@eurecom.fr
ABSTRACT connect a commercial UEs to test different configurations and net-
LTE 4G cellular networks are gradually being adopted by all major work setups and monitor the network and mobile device in realtime.
operators in the world and are expected to rule the cellular land- OAI is based on a PC hosted software radio frontend architecture.
scape at least for the current decade. They will also form the With OAI, the transceiver functionality is realized via a software
starting point for further progress beyond the current generation radio front end connected to a host computer for processing. This
of mobile cellular networks to chalk a path towards fifth generation approach is similar to other software-defined radio (SDR) proto-
mobile networks. The lack of open cellular ecosystem has lim- typing platforms in the wireless networking research community
ited applied research in this field within the boundaries of vendor such as SORA [3]. Other similar approaches combining PCs and
and operator R&D groups. Furthermore, several new approaches FPGA-based processing make use of NI LabVIEW software [4] or
and technologies are being considered as potential elements mak- using the WARP [5] architecture. To our best knowledge, OpenAir-
ing up such a future mobile network, including cloudification of Interface is the only fully x86-based SDR solution in open-source,
radio network, radio network programability and APIs following providing both UE, eNB, and core-network functionality. A simi-
SDN principles, native support of machine-type communication, lar closed-source development commercialized by Amarisoft (LTE
and massive MIMO. Research on these technologies requires real- 100) which targets several USRP platforms provides eNB and core-
istic and flexible experimentation platforms that offer a wide range network functionality on standard Linux-based PCs [6]. OAI is
of experimentation modes from real-world experimentation to con- written in standard C for several realtime Linux variants optimized
trolled and scalable evaluations while at the same time retaining for x86 and released as free software under the terms of version 3 of
backward compatibility with current generation systems. the GNU General Public License (GPLv3). OAI provides a rich de-
In this work, we present OpenAirInterface (OAI) as a suitably velopment environment with a rang of build-in tools such as highly
flexible platform towards open LTE ecosystem and playground [1]. realistic emulation modes, soft monitoring and debugging tools,
We will demonstrate an example of the use of OAI to deploy a low- protocol analyzer, performance profiler, and configurable logging
cost open LTE network using commodity hardware with standard system for all layers and channels.
LTE-compatible devices. We also show the reconfigurability fea- Towards building an open cellular ecosystem for flexible and
tures of the platform. low-cost 4G deployment and experimentations, OAI aims at the
following objectives:
Categories and Subject Descriptors • Open and integrated development environment under the con-
C.2.1 [Computer-Communication Networks]: Network Archi- trol of the experimenters;
tecture and Design - Wireless Communication System • Fully software-based network functions offering flexibility
to architect, instantiate, and reconfigure the network compo-
nents (at the edge, core, or cloud using the same or different
Keywords addressing space);
OpenAirInterface, LTE, Open Cellular Ecosystem • Playground for commercial handsets as well as application,
service, and content providers;
1. INTRODUCTION • Rapid prototyping of 3GPP compliant and non-compliant use-
cases as well as new concepts towards 5G systems ranging
Cellular systems are among one of the last industries expected to from M2M/IoT and software-defined networking to cloud-
converge from a slow-moving proprietary and expensive HW/SW RAN and massive MIMO.
platforms towards an open SW platforms leveraging commodity
hardware. This is required to build an open cellular ecosystem
and foster innovations in the wireless world as already produced 2. OPENAIRINTERFACE (OAI)
in OpenStack for cloud services and Android for mobile OS. Cur-
rently, the only open cellular ecosystem is that of OpenBTS, which 2.1 Software
provides an open development kit for 2G systems [2]. Currently, the OAI platform includes a full software implementa-
In this work, we present OpenAirInterface (OAI) wireless tech- tion of 4th generation mobile cellular systems compliant with 3GPP
nology platform as a first opensource software-based implementa- LTE standards in C under realtime Linux optimized for x86. At the
tion of the LTE system spanning the full protocol stack of 3GPP Physical layer, it provides the following features:
standard both in E-UTRAN and EPC [1]. It can be used to build
and customized an LTE base station and core network on a PC and • LTE release 8.6 compliant, with a subset of release 10;
IP packets AT commands Management (OSS)
MME Application S+P-GW Application
Linux IP
NAS eNB Application NAS HSS S11 S1-U
stack
RRC RRC S1-MME X2AP S1-U S1-MME S6a/Diameter GTP-U SGi
PDCP PDCP SCTP UDP SCTP UDP
RLC RLC IP IP
MAC MAC Ethernet Ethernet
PHY PHY
OAI soft UE OAI soft eNB OAI soft EPC (MME and S+P-GW
3GPP layers Linux stack Data Plane Control Plane
Figure 1: OpenAirInterface LTE software stack.
• FDD and TDD configurations in 5, 10, and 20 MHz band- scope. It also provide tools for protocol validation, performance
width; evaluation and pre-deployment system test. Several interoperability
• Transmission mode: 1 (SISO), and 2, 4, 5, and 6 (MIMO tests have been successfully performed with the commercial LTE-
2x2); enabled mobile devices, namely Huawei E392, E398u-1, Bandrich
• CQI/PMI reporting; 500 as well as with commercial 3rd party EPC prototypes. OAI
• All DL channels are supported: PSS, SSS, PBCH, PCFICH, platform can be used in several different configurations involving
PHICH, PDCCH, PDSCH, PMCH; commercial components to varying degrees:
• All UL channels are supported: PRACH, PUSCH, PUCCH, • OAI UE ↔ OAI eNB + OAI EPC
SRS, DRS; • OAI UE ↔ OAI eNB + Commercial EPC
• HARQ support (UL and DL); • OAI UE ↔ Commercial eNB + OAI EPC
• Highly optimized base band processing (including turbo de- • OAI UE ↔ Commercial eNB + Commercial EPC
coder). With AVX2 optimization, a full software solution
• Commercial UE ↔ Commercial eNB + OAI EPC
would fit with an average of 1x86 core per eNB instance
(64QAM in downlink, 16QAM in uplink, 20MHz, SISO). • Commercial UE ↔ OAI eNB + Commercial EPC
• Commercial UE ↔ OAI eNB + OAI EPC
For the E-UTRAN protocol stack, it provides:
2.2 Hardware
• LTE release 8.6 compliant and a subset of release 10 features; For real-world experimentation and validation, the default soft-
• Implements the MAC, RLC, PDCP and RRC layers; ware radio frontend for OAI is ExpressMIMO2 PCI Express (PCIe)
• protocol service for Rel10 eMBMS (MCH, MCCH, MTCH) board. This board features a LEON3 embedded system based on
• Priority-based MAC scheduler with dynamic MCS selection; Spartan 6 LX150T FPGA as well as 4 high-quality RF chipsets
• Fully reconfigurable protocol stack; from Lime Micro Systems (LMS6002), which are LTE-grade MIMO
• Integrity check and encryption using the AES algorithm; RF front-ends for small cell eNBs. It supports stand-alone oper-
• Support of RRC measurement with measurement gap; ation at low-power levels (maximum 0 dBm transmit power per
channel) simply by connecting an antenna to the board. External
• Standard S1AP and GTP-U interfaces to the Core Network;
RF for high-power and TDD/FDD duplexing can be connected to
• IPv4 and IPv6 support. ExpressMIMO2 depending on the deployment scenario. RF equip-
Evolved packet core network features: ment can be configured for both TDD or FDD operation with chan-
nel bandwidths up to 20 MHz covering a very large part of the avail-
• MME, SGW, PGW and HSS implementations. OAI reuses able RF spectrum (250 MHz-3.8 GHz) and a subset of LTE MIMO
standards compliant stacks of GTPv1u and GTPv2c appli- transmission modes. ExpressMIMO2 boards are reasonably-priced
cation protocols from the open-source software implementa- and completely open (GNU GPL), both at the hardware and soft-
tion of EPC called nwEPC [7]; ware level. Figure 2 shows the ExpressMIMO2 hardware platform.
• NAS integrity and encryption using the AES algorithm;
• UE procedures handling: attach, authentication, service ac- RF RX
(4 way)
cess, radio bearer establishment;
• Transparent access to the IP network (no external Serving
Gateway nor PDN Gateway are necessary). Configurable ac- RF TX
(4 way)
cess point name, IP range, DNS and E-RAB QoS;
• IPv4 and IPv6 support.
Figure 1 shows a schematic of the implemented LTE protocol PCIe (1 or 4 way)
stack in OAI. OAI can be used in the context of a rich software 4xLMS6002D RF ASICs
250 MHz – 3.8 GHz
GPIO for external
RF control
Spartan 6 LX150T 12V from ATX
power supply
development environment including Aeroflex-Geisler LEON / GR-
LIB, RTOS either RTAI or RT-PREEMPT, Linux, GNU, Wire- Figure 2: OAI ExpressMIMO2 hardware platform.
shark, control and monitoring tools, message and time analyser, The embedded software for the FPGA is booted via the PC or
low level loggin system, traffic generator, profiling tools and soft can reside entirely in the boot ROM which is part of the FPGA
HSS OAI Soft EPC OAI Soft eNB COTS UE
design. In the current design, the embedded software is booted by App MME
Server
PCIexpress dynamically under control of the PC device driver. The
basic design does not include any on-FPGA signal processing and
S11
S1
-C
consumes approximately 10-15% of the FPGA resources. There
is significant room left for additional processing on the FPGA, for
Internet SGi S1-U
instance Xilinx FFT processors to offload some processing from
GPP EXMIMO II
the host PC if required. S+P-GW
Besides ExpressMIMO2, OAI now supports the UHD interface
on recent USRP PC-hosted software radio platforms which are widely Figure 3: Demo setup and involved entities.
used in the research community. Specifically, Agilent China has re-
cently succeeded in interconnecting the OpenAirInterface softmo-
dem software with a USRP B210 platform [8]. This development
is now delivered as part of the publicly-available software pack-
age from the OAI website and SVN server [1]. EURECOM will
continue to maintain this development and extend to X300 (USRP-
Rio) family products. This achievement illustrates the validity of
the standard PC plus generic SDR frontend approach taken in OAI OAI soft eNB Huawei E398u-1 Received constellation
since the code has been independently ported successfully on a to- (PC+EXMIMO II) Dongle (2.6GHz FDD) at eNB
tally different hardware target. FDD channel emulation ASCOM TEMS
(wiring+attenuator + TX/RX filters (tracing software)
3. DEMO DESCRIPTION
Figure 4: Hardware components of the demo.
The considered demonstration scenario are depicted in Figure 3
and 4, and consists of 1 commercial LTE-enabled smartphone or 5. CONCLUSION
Dongle (Huawei ascend P7 or E398u-1) and a laptop equipped with We present the OpenAirInterface as a suitably flexible platform
a USB LTE dongle (Huawei E398u-1 or Bandrich C500), 1 OAI for an open cellular ecosystem both for 4G experimentation as well
soft eNB and 1 OAI soft EPC running on the top of Intel-based as for 5G research. It offers an open-source reference software
PC(s). Different setups are possible ranging from an all-in-one implementation of 3GPP-compliant LTE system and a subset of
PC to all in a physically separated entities, which are deployment- LTE-A features for real-time indoor/outdoor experimentation and
specific. For the demo, we plan to demonstrate an all-in-one setup, demonstration.
where OAI soft eNB and EPC functions are performed inside the In the demo, we present an all-in-one LTE network deployment
same PC. In such a configuration, eNB is running on the host PC in a PC based on OpenAirInterface platform. We show the inter-
under realtime Linux, MME and S+P-GW running on the top of a operability with commercial LTE enabled USB dongle and smart-
VM, and HSS in another VM. phones highlighting the complete attach procedure, establishment
The demonstration will be deployed in FDD SISO mode. Two of default data radio bearer, and a live video transmission in down-
target frequencies will be used: band 13 (USA) and band 7 (Eu- link. We also show the reconfigurability features of the platform.
rope) in a controlled indoor radio environment. In the proposed
demonstration, we will assess the following objectives Acknowledgement
The research and development leading to these results has received
• Successful attach procedure (control-plane), and video stream- funding from the European Research Council under the European
ing in downlink (data-plane); Community Seventh Framework Programme (FP7/2014- 2017) grant
• High-level of reconfigurability and programmability span- agreement 612050 FLEX project and 318306 NEWCOM# project.
ning all the layers allowing all kind of setups from protocols
to radio frequency; 6. REFERENCES
[1] The OpenAirInterface Platform. Web: www.openairinterface.org/,
• demonstrate the mobile device behaviour in realtime; Repository: svn.eurecom.fr/openair4G/trunk.
• Usage of commodity hardware to run LTE network in a PC. [2] OpenBTS Project. www.openbts.org/.
[3] K. Tan and al. Sora: High-Performance Software Radio Using
The aforementioned experimental scenario will be demonstrated General-Purpose Multi-Core Processors. Communications of the
in live and the obtained results will be presented in parallel with the ACM, 2011.
experiment execution. We will discuss the network programmabil- [4] S. Shearman and al. Software Defined Radio Prototyping Platforms
Enable a Flexible Approach to Design. IEEE Microwave Magazine,
ity/reconfigurability through open APIs as well as the usage of OAI
2012.
in both small-cell and cloud-RAN centralized processing. [5] K. Amiri and al. Warp, a unified wireless network testbed for
education and research. In Proceedings of IEEE MSE, 2007.
4. DEMO REQUIREMENTS [6] Amarisoft. www.amarisoft.com/.
The following equipments will be used for the demonstration: [7] nwEPC - EPC SAE Gateway. http://sourceforge.net/projects/nwepc/.
[8] Ettus USRP B210. www.ettus.com/product/details/UN210-KIT.
• a PC running OAI EPC and OAI eNB with EXMIMOII card;
• one LTE UE dongle and one LTE smartphone;
• cables, filters, small antenna and attenuators.
In addition, we also require:
• a desk of 3 meters length to place the equipment;
• power supply plugs for all the devices and Internet access;
• 5 to 10 minutes to show and explain the demo.
