The Open Base Station Architecture Initiative (OBSAI) was a trade association created by

Hyundai Hyundai is a former South Korean industrial conglomerate ("''chaebol''"), which was restructured into the following groups: * Hyundai Group, parts of the former conglomerate which have not been divested ** Hyundai Asan, a real estate construction ...

LG Electronics LG Electronics Inc. () is a South Korean Multinational corporation, multinational major appliance and consumer electronics corporation headquartered in Yeouido-dong, Seoul, South Korea. LG Electronics is a part of LG, LG Corporation, the fourth ...

Nokia Nokia Corporation is a Finnish multinational corporation, multinational telecommunications industry, telecommunications, technology company, information technology, and consumer electronics corporation, originally established as a pulp mill in 1 ...

Samsung Samsung Group (; stylised as SΛMSUNG) is a South Korean Multinational corporation, multinational manufacturing Conglomerate (company), conglomerate headquartered in the Samsung Town office complex in Seoul. The group consists of numerous a ...

and

ZTE ZTE Corporation is a Chinese partially state-owned technology company that specializes in telecommunication. Founded in 1985, ZTE is listed on both the Hong Kong and Shenzhen Stock Exchanges. ZTE's core business is wireless, exchange, opti ...

in September 2002 with the aim of creating an open market for

cellular network A cellular network or mobile network is a telecommunications network where the link to and from end nodes is wireless network, wireless and the network is distributed over land areas called ''cells'', each served by at least one fixed-locatio ...

base stations. The hope was that an open market would reduce the development effort and costs traditionally associated with creating base station products.

Goal

The OBSAI specifications provided the architecture, function descriptions and minimum requirements for integration of a set of common modules into a

base transceiver station A base transceiver station (BTS) or a baseband unit (BBU) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phone A mobile phone or cell phone is a portab ...

(BTS). It: * defined an internal modular structure of wireless base stations. * defined a set of standard BTS modules with specified form, fit and function such that BTS vendors can acquire and integrate modules from multiple vendors in an OEM fashion. * defined internal digital interfaces between BTS modules to assure interoperability and compatibility. * supported different access technologies such as

GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...

Enhanced Data Rates for GSM Evolution Enhanced Data rates for GSM Evolution (EDGE), also known as 2.75G and under various other names, is a 2G digital mobile phone technology for packet switched data transmission. It is a subset of General Packet Radio Service (GPRS) on the G ...

(EDGE),

CDMA2000 CDMA2000 (also known as C2K or IMT Multi‑Carrier (IMT‑MC)) is a family of 3G mobile technology standards for sending voice, data, and signaling data between mobile phones and cell sites. It is developed by 3GPP2 as a backwards-compatib ...

WCDMA The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses wideband code-division multiple access (W- CDMA) radio access technology to offer greater spectral efficienc ...

IEEE 802.16 IEEE 802.16 is a series of wireless broadband standards written by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE Standards Board established a working group in 1999 to develop standards for broadband for wireless metropo ...

marketed as

WiMAX Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options. The WiMA ...

. This was intended to provide the BTS integrator with flexibility. A version 2.0 system reference document was published in 2006.

BTS structure

The OBSAI Reference Architecture defines four functional blocks, interfaces between them, and requirements for external interfaces.

Functional blocks

A base transceiver station (BTS) has four main blocks or logical entities:

Radio Frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the u ...

(RF) block,

Baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into ...

block, Control and Clock block, and Transport block. The Radio Frequency Block sends and receives signals to/from portable devices (via the air interface) and converts between

digital data Digital data, in information theory and information systems, is information represented as a string of Discrete mathematics, discrete symbols, each of which can take on one of only a finite number of values from some alphabet (formal languages ...

and antenna signal. Some of the main functions are D/A and A/D conversion, up/down conversion, carrier selection, linear power amplification,

diversity Diversity, diversify, or diverse may refer to: Business *Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce *Diversity marketing, marketing communication targeting diverse customers * ...

transmit and receive, RF combining and RF filtering. The Baseband Block processes the baseband signal. The functions include encoding/decoding, ciphering/deciphering, frequency hopping (GSM), spreading and

Rake receiver A rake receiver is a radio receiver designed to counter the effects of multipath fading. It does this by using several "sub-receivers" called ''fingers'', that is, several correlators each assigned to a different multipath component. Each finger ...

(WCDMA),

MAC Mac or MAC may refer to: Common meanings * Mac (computer), a line of personal computers made by Apple Inc. * Mackintosh, a raincoat made of rubberized cloth * Mac, a prefix to surnames derived from Gaelic languages * McIntosh (apple), a Canadi ...

(WiMAX), protocol frame processing,

MIMO In radio, multiple-input and multiple-output (MIMO) () is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wirel ...

etc. The Transport Block interfaces to external network, and provides functions such as QoS, security functions and synchronization. Coordination between these three blocks is maintained by the Control and Clock Block.

Internal interfaces

Internal interfaces between the functional blocks are called reference points (RP). RP1 is the interface that allows communication between the control block and the other three blocks. It includes control and clock signals. RP1 specification also specifies UDPCP - a UDP based reliable communication protocol. A version 2.1 of the reference point 1 interface was published in 2008. RP2 provides a link between the transport and baseband blocks. Version 2.1 of the reference point 2 interface was published in 2008. RP3 is the interface between baseband block and RF block. RP3-01 is an (alternate) interface between Local Converter and Remote RF block. Version 4.2 of the reference point 3 interface was published in 2010. RP4 provides the DC power interface between the internal modules and DC power sources. Version 1.1 of the reference point 4 interface was published in 2010. Most of the industry at the time revolved around achieving lower cost RF modules and power amplifiers (PA), as these two components usually account for nearly 50 percent of the BTS cost. Consequently, OBSAI works to define reference point 3 (RP3) prior to the other reference points to promote more competitive sources in the RF module and PA market.

External interfaces

Transport Block provides external network interface to operator network. Examples are: (lub) to the

Radio Network Controller The Radio Network Controller (RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some of the mobility managem ...

(RNC) for

3GPP The 3rd Generation Partnership Project (3GPP) is an umbrella term for a number of standards organizations which develop protocols for mobile telecommunications. Its best known work is the development and maintenance of: * GSM and related 2G and ...

systems, R6 to the Access Services Network Gateway (centralized Gateway) or R3 to Connectivity Services Network (CSN) for WiMAX systems. RF Block provides external radio interface to subscriber devices. Examples are Uu or Um to the

user equipment In the Universal Mobile Telecommunications System (UMTS) and 3GPP Long Term Evolution (LTE), user equipment (UE) is any device used directly by an end-user to communicate. It can be a hand-held telephone, a laptop computer equipped with a mobile b ...

(UE) for

systems or R1 for WiMAX.

References