Bss Base Station Subsystem: Module Objectives

BSS Base Station Subsystem Module Objectives: BSS architecture Purpose Elements in BSS Who maintains the StandardsUses and functioning of element BSS maintenance Understanding of Interfaces Questionnaire Examples with pictures

BSS Architecture

• BSS is a RAN-Radio Access Network • Why RAN?????? PURPOSE: • Its purpose is to manage the radio link between mobile phones and a telecommunication core network. Different Types of Access Networks: • In GSM it is called as GRAN-GSM Radio Access Network.-It provides access to both Circuit switched (CS) and Packet switched (PS) core networks.

• GERAN-GERAN is the radio part of GSM/EDGE Network. It is essentially the same as GRAN

but specifying the inclusion of EDGE packet radio services. A mobile phone operator's network comprises one or more GERANs-through which phone calls and packet data are routed from and to the PSTN and Internet to and from subscriber handsets. • The standards for GERAN are maintained by the 3GPP. • UTRAN-UMTS radio access network

Note: It is also possible for a single handset/phone to be simultaneously connected to multiple radio access networks. Handsets capable of this are sometimes called dual-mode handsets. For instance it is common today (2008) for handsets to support both GSM and UMTS (a.k.a. "3G") radio access technologies. It is then possible to seamlessly transfer an ongoing call between different radio access networks without the user noticing any disruption in service

BSS elements • One or more BTSs (Base Transceiver Station) • One BSC (Base Station Controller) • One TRAU (Transcoding Rate and Adaptation Unit)

References: • IS-54 and IS-136 are second-generation (2G) mobile phone systems, known as Digital AMPS (D-AMPS). It was once prevalent throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000 technologies. • Interim Standard 95 (IS-95) is the first CDMAbased digital cellular standard pioneered by Qualcomm. The brand name for IS-95 is cdmaOne. IS-95 is also known as TIA-EIA-95. • 3GPP-UMTS/EDGE

• The BTS houses the radio transceivers that define a cell and handles the radio link protocols with the MS. • BTS contains the equipment for transmitting and receiving of radio signals (between BSC and MS), antennas, equipment for modulation, encrypting and decrypting communications with the BSC.

BTS and Cell

•The BTS corresponds to the transceivers and antennas used in each cell of the network

• Its transmitting power defines the size of a cell . • Each BTS has between 1 and 16 transceivers, depending on the density of users in the cell. This is achieved by sectorization. • Each BTS serves a single cell.

• A base transceiver station (BTS) or cell site is a physical site that facilitates wireless communication between the user equipment (UE) and a network. • UEs are devices like handsets, WLL phones, computers with wireless internet (Data Card) connectivity, WiFi and WiMAX gadgets etc. The network can be that of any of the wireless communication technologies like GSM,CDMA, WLL, WAN, WiFi and WiMAX etc. . • In GSM it is communication in uplink and downlink directions

• BTS is also referred to as the radio base station (RBS), node B (in 3G Networks) or, simply, the base station (BS). For discussion of the LTE standard the abbreviation eNB for enhanced node B is widely used.

Architecture of a BTS • equipment for encrypting and decrypting communications . antennas they facilitate the functioning of BTS . • TRXs which serve several different frequencies in different sectors of the cell (in the case of sectorised base stations). • A BTS is controlled by a parent base station controller via the base station control function (BCF) . The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations is it a card????

• Transceiver (TRX) also called as (DRX) driver receiver. • Power amplifier (PA)-Amplifies the signal from DRX for transmission through antenna; may be integrated with DRX. • Combiner – Combines I/O feeds from several TRXs. So that they could be sent out through a single antenna. Allows for a reduction in the number of antenna used.

• Duplexer – For separating sending and receiving signals to/from antenna. Does sending and receiving signals through the same antenna ports (cables to antenna).

• Antenna: For Transmission of the signals. • Alarm extension system – Collects working status alarms of various units in the BTS and extends them to operations and maintenance (O&M) monitoring stations. • Control function – Control and manages the various units of BTS including any software. On-the-spot configurations, status changes, software upgrades, etc. are done through the control function. • Base band receiver unit (BBxx): Frequency hopping, signal DSP, etc..

Functions • Encoding, encrypting, multiplexing, modulating, and feeding the RF signals to the antenna. • Transcoding and rate adaptation • Time and frequency synchronizing • Voice through full- or half-rate services • Decoding, decrypting, and equalizing received signals • Random access detection • Timing advances • Uplink channel measurements

BTS Structure

BTS Structure

BTS Structure

SC4812T-MC BTS

• BTS Tower • BTS Shelter

• The BTS and the BSC communicate across the specified Abis interface, enabling operations between components that are made by different suppliers.-Means BTS and BSC can be from two different manufacturer. • A separate high-speed line (T1 or E1) is then connected from the BSS to the Mobile MSC.

• BTS Shelter

• BTS includes a BTS cabinet and one or more extension cabinets depending on BTS type. • No of cabinets depend on number of Radio Channels to be supported and the site structure (single or multi-cellular site).

Functions • Encoding, encrypting, multiplexing, modulating, and feeding the RF signals to the antenna. • Transcoding and rate adaptation • Time and frequency synchronizing • Voice through full- or half-rate services • Decoding, decrypting, and equalizing received signals • Random access detection • Timing advances • Uplink channel measurements

• BSC includes a control cabinet and equipment cabinet. The amount of constituent modules depend on no of PCM links to be managed.

BSC Functions • frequency hopping, handover, performs radio signal management functions for base transceiver stations, frequency assignment and handoff ,traffic measurement. • Power Control

TCU • TCU cabinet contains shelves managing PCM links. • No of shelves depend on no of PCM links to be connected to MSC.

TRAU-Transcoding and Rate Adaptation Unit (TRAU) • Also called as TCU(transcoder units) • TRAU, inserted between the BSC and MSC, enables speech compression and data rate adaptation . • The TRAU is designed to reduce transmission costs by minimizing transmission resources between the BSC and MSC. HOW • This is achieved by reducing the number of PCM links going to the BSC, since four traffic channels can be handled by one PCM time slot.

What does BTS Do?? • BTS broadcasts information about its identity on a channel (BCCH). • • • • •

Mobile monitors this channel so that mobile will know to which cell it belongs to and the Location area (LA) - is a group of cells. Location Update/Registration: Authentication. Radio Transmission Measurements.-Measurements include Power level, Interference, Quality of the link. Based on these Measurements: - Power Control - Call clearing - Inter cell-b/w BTS’s - Intra cell-b/w the sectors